The big thing to remember is that you've got a big toolbox with tools for just about every situation. Not only are you a full spellcaster with a wide array of spells (mostly focused around battlefield control, support, and non-combat utility, though not solely), you've also got the insane versatility of wild shape at your disposal.
Druids are prepared spellcasters, and the best way to play a prepared caster is to, well, be prepared. Since you can swap out your whole spell list every long rest, try to make educated guesses about which spells will come in the most handy on a given day. I'm a controller at heart, but I still prefer to have a good variety of spells to cover as many bases as possible.
Wild shape is, in my opinion at least, the feature that you'll be using the most - possibly even more than your spells. If there's a situation that can be solved with either spells or wild shape, my personal preference is to use wild shape, because it comes back on a short rest whereas spells come back on a long rest. It's incredibly versatile, too. Make sure you know the mechanics well and have a good handle on whichever forms you plan on using.
In combat, a common strategy is to cast a big concentration spell and then wild shape. Spells such as flaming sphere or heat metal are good for this because they give you a solid use for your bonus action, which you wouldn't be using in wild shape anyway. Spells like moonbeam and call lightning work similarly, but require your action rather than your bonus action.
It's also important to keep in mind that, unless you choose circle of the moon, your wild shape options probably aren't durable enough to be worth using as a frontline attacking option. You can still do that if you want, but it's generally not recommended.
As for spells, you'll want to become very familiar with two spells in particular: goodberry and pass without trace, because they're some of the best spells at your disposal. Familiarize yourself with all your spells, of course, but those two stand out especially.
With goodberry, the strategy is to use all of your remaining spell slots right before a long rest to cast goodberry, because they last 24 hours so you can have them the next day after you've regained all your spell slots. My level 2 wildfire druid does this and routinely has 30 HP worth of healing that she can just dole out as needed outside of combat, before expending any resources.
A life cleric dip makes this even better due to disciple of life affecting each berry. My current plan for my druid is to dip life cleric at level 4, which would give me potentially 160 hp (40 per 1st level spell slot x 4) of healing to dole out in increments of 4, and 150 hp (50 per 2nd level spell slot x 3) to dole out in increments of 5, for a total of 310 hp to just give out to people the next day without expending any resources.
With pass without trace, say hello to surprise and goodbye to alerting the guards before you're ready. With a +10 to stealth, even the full plate paladin can get the jump on enemies most of the time. Being able to surprise enemies can swing the battle immensely in the party's favor, giving the party a full round to attack the enemies without interference.
This is a big question. Is it referring to just combat, or does it also refer to roleplay?
In regards to combat generally and regardless of subclass, druids are spellcasters with a lot of different tools for many situations. For this class, their strength is in their powerful battlefield control & summoning spells, like Entangle, Faerie Fire, Conjure Animals, etc. I would say that looking for opportunities to cast one of those encounter-defining spells as soon as possible is a good call. Don’t forget that druids are prepared casters, so you can completely change up your spells every long rest.
One thing to note though is that almost all of the Druid’s most powerful spells require concentration. Typically when you play a druid, you will be dropping a single, high-impact concentration spell, and then resorting to either cantrips or the dodge action for the rest of the encounter for as long as you can keep the spell up. Druids get very few spells that will let them do damage or control of any sort without requiring their concentration. Keep that in mind when considering ASI level-ups and feats. War Caster and Resilient:Con are pretty high priority on any caster that relies on concentration and can afford to take a feat.
Another piece of general druid advice is that Wild Shape is probably best used for utility and not combat, unless you’re a Moon Druid, or playing a subclass that relies on an alternative use for it, like Stars or Wildfire. If you play with Tasha’s Cauldron rules allowed, you can use Wild-Shape to cast Find Familiar instead.
Druid playstyles can vary so much depending on the subclass you take and the spells you prepare.
Moon - Allows you to tank & frontline in melee for a time thanks to combat Wildshape. The strat falls off a bit after Level 5 until around Level 10, then falls off again until Level 18 - 20.
Land - Allows you to really focus on the Druid’s spellcasting. You get to recover spell slots and get access to a lot of useful utility spells that Druids normally don’t get. Like Haste.
Dreams - Allows you to support the party a little better with a very versatile healing ability, a bit of extra protection during rests, and a bit of team-wide mobility & teleportation. (I honestly…don’t really recommend this subclass though.)
Shepherd - Bolsters the Druid’s summoning and offers very solid AoE, team-wide support via the totems.
Stars - Boosts all the major strengths of the druid (Damage, Concentration spells, and healing). Jack of all trades, master of all.
Wildfire - Gives you unprecedented mobility for yourself and your team with the teleport. Its also one of the only druid subclasses that gives you damaging spells that don’t require concentration. (Burning hands, scorching ray)
Spores - Lets the druid be a tanky spell-caster, but with a bit more freedom to weave in and out of melee. Its a tricky subclass to play. The subclass is marketed as a “melee druid”, but don’t take the bait. This druid functions better as a tankier spellcaster first and a melee front-liner second unless you plan to multiclass it, are playing a tortle, or are playing at Levels 1-5.
Blighted - Technically not official, but its a Critical Role subclass that offers team-wide damage boosting. I vouch for it because it looks to be very solid and well-designed, with a lot of fun flavor baked into the subclass.
all there on the tin
¯\_🤠_/¯
The big thing to remember is that you've got a big toolbox with tools for just about every situation. Not only are you a full spellcaster with a wide array of spells (mostly focused around battlefield control, support, and non-combat utility, though not solely), you've also got the insane versatility of wild shape at your disposal.
Druids are prepared spellcasters, and the best way to play a prepared caster is to, well, be prepared. Since you can swap out your whole spell list every long rest, try to make educated guesses about which spells will come in the most handy on a given day. I'm a controller at heart, but I still prefer to have a good variety of spells to cover as many bases as possible.
Wild shape is, in my opinion at least, the feature that you'll be using the most - possibly even more than your spells. If there's a situation that can be solved with either spells or wild shape, my personal preference is to use wild shape, because it comes back on a short rest whereas spells come back on a long rest. It's incredibly versatile, too. Make sure you know the mechanics well and have a good handle on whichever forms you plan on using.
In combat, a common strategy is to cast a big concentration spell and then wild shape. Spells such as flaming sphere or heat metal are good for this because they give you a solid use for your bonus action, which you wouldn't be using in wild shape anyway. Spells like moonbeam and call lightning work similarly, but require your action rather than your bonus action.
It's also important to keep in mind that, unless you choose circle of the moon, your wild shape options probably aren't durable enough to be worth using as a frontline attacking option. You can still do that if you want, but it's generally not recommended.
As for spells, you'll want to become very familiar with two spells in particular: goodberry and pass without trace, because they're some of the best spells at your disposal. Familiarize yourself with all your spells, of course, but those two stand out especially.
With goodberry, the strategy is to use all of your remaining spell slots right before a long rest to cast goodberry, because they last 24 hours so you can have them the next day after you've regained all your spell slots. My level 2 wildfire druid does this and routinely has 30 HP worth of healing that she can just dole out as needed outside of combat, before expending any resources.
A life cleric dip makes this even better due to disciple of life affecting each berry. My current plan for my druid is to dip life cleric at level 4, which would give me potentially 160 hp (40 per 1st level spell slot x 4) of healing to dole out in increments of 4, and 150 hp (50 per 2nd level spell slot x 3) to dole out in increments of 5, for a total of 310 hp to just give out to people the next day without expending any resources.
With pass without trace, say hello to surprise and goodbye to alerting the guards before you're ready. With a +10 to stealth, even the full plate paladin can get the jump on enemies most of the time. Being able to surprise enemies can swing the battle immensely in the party's favor, giving the party a full round to attack the enemies without interference.
This is a big question. Is it referring to just combat, or does it also refer to roleplay?
In regards to combat generally and regardless of subclass, druids are spellcasters with a lot of different tools for many situations. For this class, their strength is in their powerful battlefield control & summoning spells, like Entangle, Faerie Fire, Conjure Animals, etc. I would say that looking for opportunities to cast one of those encounter-defining spells as soon as possible is a good call. Don’t forget that druids are prepared casters, so you can completely change up your spells every long rest.
One thing to note though is that almost all of the Druid’s most powerful spells require concentration. Typically when you play a druid, you will be dropping a single, high-impact concentration spell, and then resorting to either cantrips or the dodge action for the rest of the encounter for as long as you can keep the spell up. Druids get very few spells that will let them do damage or control of any sort without requiring their concentration. Keep that in mind when considering ASI level-ups and feats. War Caster and Resilient:Con are pretty high priority on any caster that relies on concentration and can afford to take a feat.
Another piece of general druid advice is that Wild Shape is probably best used for utility and not combat, unless you’re a Moon Druid, or playing a subclass that relies on an alternative use for it, like Stars or Wildfire. If you play with Tasha’s Cauldron rules allowed, you can use Wild-Shape to cast Find Familiar instead.
Druid playstyles can vary so much depending on the subclass you take and the spells you prepare.
Moon - Allows you to tank & frontline in melee for a time thanks to combat Wildshape. The strat falls off a bit after Level 5 until around Level 10, then falls off again until Level 18 - 20.
Land - Allows you to really focus on the Druid’s spellcasting. You get to recover spell slots and get access to a lot of useful utility spells that Druids normally don’t get. Like Haste.
Dreams - Allows you to support the party a little better with a very versatile healing ability, a bit of extra protection during rests, and a bit of team-wide mobility & teleportation. (I honestly…don’t really recommend this subclass though.)
Shepherd - Bolsters the Druid’s summoning and offers very solid AoE, team-wide support via the totems.
Stars - Boosts all the major strengths of the druid (Damage, Concentration spells, and healing). Jack of all trades, master of all.
Wildfire - Gives you unprecedented mobility for yourself and your team with the teleport. Its also one of the only druid subclasses that gives you damaging spells that don’t require concentration. (Burning hands, scorching ray)
Spores - Lets the druid be a tanky spell-caster, but with a bit more freedom to weave in and out of melee. Its a tricky subclass to play. The subclass is marketed as a “melee druid”, but don’t take the bait. This druid functions better as a tankier spellcaster first and a melee front-liner second unless you plan to multiclass it, are playing a tortle, or are playing at Levels 1-5.
Blighted - Technically not official, but its a Critical Role subclass that offers team-wide damage boosting. I vouch for it because it looks to be very solid and well-designed, with a lot of fun flavor baked into the subclass.
Hope that helped a bit.
Thanks pardner ya'll helped me a lot both of y'all
¯\_🤠_/¯