Give the players options! But don't. Ask them a simple question. Like Which town would you like to go to? Or, Which bounty do you all decide on? 

Truth is, they are all the same bounty/town. This gives the players a sense of choice and freedom whilst you don't have to prepare several encounters.

Quote from XavisDOS >>

How do you guys avoid railroading the players while making sure you are able to be prepared and not improvising terribly? I am sure there is a simple solution but I haven't found it :/

Yeah, the simple solution is to stop worrying about it. :-) 

Every game is going to have some degree of railroading, and the players have agreed to this by choosing to sit at the table.

Have a discussion about it. Tell the players outright, "I've got good plans for this and this, and vague plans for that and that, so your characters need to pick one of these four options." If a player insists on something else, tell them to stop breaking Wheaton's Law. 

If you are OK with going off-track then be honest with the players. "If you pick another option, I'll have a go at it, but my improvisation sucks so you are just not going to get as good a game. Your choice."

Figure out what would happen if the pcs werent there, when you know that, you can kind of improvise how people will act/react when nudged by the pcs (interaction is them nudging the world from 'the timeline')

Get those world building supplements and read them. Or read a lot of heroic fantasy litterature (e.g. Conan by R.E.Howard, that's an excellent source for D&D inspiration..). In these supplements and/or litterature you'll find a lot of good ideas for adventures that wont really directly fit into your main campaign, but still fit in universe and look fun and epic.

Keep those in a corner of your mind or in your GM notes, and then when your players veer off track bring the one that seems the most relevant, or most fun, or both out and enjoy :) 

Two thing that work at our table to help with this;

1) The players communicate where they are intending to go before the next session.  This gives the DM adequate time to prep.  so if we end a session at either a crossroads in a dungeon, or the party could go to different towns; don't keep that a secret from the DM.

2) Our DM designs the adventure from the back forward.  So the ending of each adventure is very detailed, and he continues to flesh out the details moving backwards until it is clear which story direction the group is taking.  So it is a sandbox that does not railroad, but it also means the DM is not preparing for things that group just doesn't investigate.    

Never be afraid to say "Yes I can give you information on that, but I haven't written it yet and it's not relevant right now, so I'll sort that out between sessions!"

This has saved me from A: having to stop a session to make up a lore dump on the spot, B: getting my lore wrong and not tying in important details, meaning I have to add them in after, making them really obviously important, and C: taking up session time explaining something that only one player is interested in!

Part of the job of the DM is to maintain session pacing, so if one or two players are set on exploring every shop and talking to every NPC whilst everyone else is drumming their fingers or losing interest then you need to chivvy them along: "For the sake of getting somewhere this session, we can cover this in between games on the Discord chat". 

Anyway, for railroading without railroading, the important things I maintain are:

1: Remind them what they are doing at the start of each session. If they have been chased to a town by a bandit bounty hunter, and you start the session in the town, remind them how they got there - they don't want to get side-tracked when they're being chased. 9 times out of 10, if you're htinking "wow, this is a silly thing to do whilst they are being chased" or something, then they would think the same if they remembered that they were being chased. a simple "are you sure you want to go shopping, I know it's been a fortnight for us but your characters have just arrived in town with an enemy hot on their heels!" can re-center the players on the adventure in hand!

2: Allow them to wander, but don't let the world pause for them. This isn't skyrim - if someone says they'll meet you by the temple, then coming back 8 weeks later will not find them stood idly still waiting for you! Similarly, if the party goes off on a tangent the BBEGs plans will keep moving forward! Seeing consequences for their delays will keep them moving - in my campaign, they found a dragons horde, then spent several days in town organising wagons, and then checking in with the bank, and then inventing some stuff, running some errands, doing some downtime, then traveled back to the dragons lair to find Giants removing the last of the horde.

3: If there is an obvious choice, only plan roughly what will happen. I made the mistake of planning a route down a river, and used an old, outdated map I made years ago to draw the river on. The party immediately saw an old mark on the map that said "abandoned fortress" in the middle of a cursed moor, and decided they wanted to go that way instead! I hadn't planned that route at all, and the mark on the map was something I put in to fill the gap back when I first drew it. I've since fleshed it out some, and they were persuaded to stay on the river, but it was a close call to invalidate all the work I had done on the river! So now, if they have a choice of routes, I will try to get them to pick one at the end of, or between, sessions, so that I can plan it out before the next session starts! This keeps you from overplanning, and lets you keep "they meet important NPC number 4 in..." blank until they decide to go via Riverbrook, in which case it becomes "Important NPC number 4 in Riverbrook". This way you can lay the plothooks you need out in front of them, whilst maintaining a feeling of freedom and exploration.

In my upcoming campaign, there are exactly two times when I will railroad characters:  The very start of the game (getting them all in the same place to start with) and then later in the overall storyline when they are captured and forced to do a job.

It has been the longest period of time for campaign creation in my life -- 4 years so far, with this year being the fifth and final -- but the objective is to allow them to do whatever they hell they want to do, honestly.

This is a Campaign with 21 adventures, each for a single level, using a combination of milestones and a hero points mechanics. They follow a set story that has a crapton of subplots interwoven throughout it (including a Princess that needs rescuing at then later on a crowning, a group of rivals who are all pastiches of the PCs themselves, relationship [friend/romance] subplots, and more). The assorted stories and experiences actually have an impact on the world at large (for example, if they fail to save the princess, then that bad guy becomes big bad #2 and will cause them more problems and ultimately turn the world against the players), and so yeah, I kinda sorta really want them to go through it, lol.

I have a crapton of side quests that are just "there". Some are even merely hints of side quests mostly set up for window dressing.

For each and every Adventure, there are at least three story hooks. I know my players, but even they can sometimes be contrary, lol, so for each story Hook I also have "bait" -- something I know the characters will want or think they want, and for each hook there is at least five bits of bait.  Magic items are great bait for hooks.

I also have 20 little stories that are not part of the main adventure, and there are 35 errands and forty side quests.  In short, it is a lot, and it is simply set up.  Some of the errands and side quests (not all, just some) have additional links back to the main story, and of course I have the rivals to really encourage them because if they don't do something the rivals do, and they love to brag and rub it in and be annoying.

That's my part. I plan a two year campaign and let it be.  I am making notes for the next campaign, in "unexplored areas", but they are just notes. From the point we start playing, my job will be to make what they do have meaning for them.

I hedge my bets, of course -- this is a pure homebrew set up.  At every step of the development and design stage I have asked them for feedback -- and the start of it is based in them wanting something new, and I have taken all their suggestions and done my absolute best to meet them (though not always to their complete satisfaction). and they know I have worked my butt off at this, lol, so I think they will bite the hooks and all -- I mean, they suggested some of the adventures. I just had to put them together into a story that was layered, fit together, fit the world, made sense, and was actually achievable.

But really, with all of that stuff just sitting there waiting, and knowing all of the material, I don't stress it because I can always drop in a thing that links this weird romp they opted to take into the unexplored lands into something that gives them a reason to do the campaign. 

The first adventure was supposed to have them as children in flashbacks so they play as kids, but one of them wants to be a special type of warforged style (and gets away with the ask because I also had to include the HZD machine animals) and that means I have to drop the kid part (though I really do love it) and add the "adult portion" of that first adventure to a later segment.  ALl of the chapters are like that, though -- I can flex them according to the needs of the players.

And if it sounds like I am saying the role of a DM is to just let players do whatever and have more control, I apologize, I am not saying that. I am the final arbiter, the moderator, the  embodiment of destiny and fate and whatever, and my job is not to push them anywhere, but to lay out the path for them and then apply consequences for every time they don't go down that path, lol.

They will get there eventually.  And in the meantime, we can have fun and they can figure out the aspect of their characters they want to explore and I can just be playing the NPCs and we can explore the world together. Because even with all that work I did to create it, I still don't fully get it from the street level. And won't until we are all there, looking at the weird ass thatched hut and thinking "why are those carrots so damn big".

So the best way to avoid railroading is to not try to. Set parameters at the zero session. Know your players. Be creative. have fun. Relax.

You won't ruin it.

Quote from AEDorsay >>

and then later in the overall storyline when they are captured and forced to do a job. 

As always, do this with extreme caution.

Some players do not take well to being captured. They will fight to the death, they will make poor choices, some will feel real life triggers, and ultimately they can feel betrayed if they even get a hint that the whole point was to get them captured no matter what they did.

Quote from Wysperra >>

Quote from AEDorsay >>

and then later in the overall storyline when they are captured and forced to do a job. 

 

As always, do this with extreme caution.

Some players do not take well to being captured. They will fight to the death, they will make poor choices, some will feel real life triggers, and ultimately they can feel betrayed if they even get a hint that the whole point was to get them captured no matter what they did.

 Yes, and since my folks are very big on role play, it can get pretty wild. 

It does help that their DM has been through multiple traumas and has been a licensed therapist and already knows all their triggers, lol.  Well, for the most part -- the new group might be a little more chill.

Fortunately it is a "lights go out and you wake up before the lord" style deal. full on Deus Machina.