Advice for level 1 homebrew campaign

Hello everyone! I just finished dm'ing a pre written module and it was my first time as a Dm. I am now getting the itch to run a homebrew campaign in my own setting. I have an overall handle on making my world and fleshed out the starting area. My main question is- Should I run a few starter/side quests that really do not link to anything and see what my party likes then flesh out the story from there and maybe create a bbeg based on how the interact with things those first few sessions OR should I know what my bbeg is first and then have everything link (as best as possible because we all know nothing goes as planned in DND). This will start at level 1 and I am planning on a long term campaign. 

Any advice is greatly appreciated!

in my opinion you should start with the miscellaneous starter quests while having a basic bbeg idea and shape it according to your parties choices

at least that's what I have done sometimes. other times I improvised almost everything from a basic outline  

Thank you! 

Rather than deciding on a BBEG right off the bat, I would suggest deciding on a theme first. Then make a short list of what sorts of BBEGs might fit that theme. Then, as BTB suggested, toss a bunch of plot hooks at the players to see which ones they bite on. Develop the plot in response to the attention that the players show toward certain hooks or certain NPCs. And make a note of which NPCs the players grow attached to, so you can devise ways to make them either agents of the BBEG who will turn on the players, or victims of the BBEG who will be sacrificed to propel your players into the Final Battle.

Try to write in your character's backstories into the campaign. Like suggested above, it is also good to get a general idea of what the campaign's theme will be (High Fantasy, Horror). Another thin to do that I wished I had done with my players was to have them create connections on how they know some or all of each other. It opens up roleplaying opportunities and makes it much easier to start without going through the process of having them come together as a group-they already know each other. 

For a start, I recommend having them do some odd jobs, delve into some dungeons, and do a couple other things that seem rather unrelated, but drop some foreshadowing or hooks into later ideas you have and maybe some future planned villains.

Quote from WolfeCriedPup >>

Try to write in your character's backstories into the campaign. Like suggested above, it is also good to get a general idea of what the campaign's theme will be (High Fantasy, Horror). <snip>

For a start, I recommend having them do some odd jobs, delve into some dungeons, and do a couple other things that seem rather unrelated, but drop some foreshadowing or hooks into later ideas you have and maybe some future planned villains.

I strongly recommend tying the character's backstories into the campaign as well, but I would suggest trying to avoid making the overall story arc personal for only one character. If the character dies or the player wants to play another character, your whole plot is suddenly standing on nothing. Sure, the BBEG can be more meaningful and personal to some character initially, but make it somehow personal for the other characters as well. Maybe the BBEG destroyed one character's hometown, maybe they know – if not directly responsible  – the truth about another character's lost ancestry, and so on.

As they start at level 1, the first quests should be quite local and "trivial" in the big scale, but should have some hints of events to come. The sheep that ran amok as their first quest were scared by a band of goblins. But the goblins were taking orders from an ogre, who in turn took orders from a giant. The giant was being controlled by an evil lich, who is the BBEG's henchman. And the BBEG is a demon from the Abyss trying to succumb the whole material plane to the will of demons. Or something similar, I made this up as I was typing. I had no idea I would end up in demons when I started with sheep running amok.

And circling back to the first paragraph with the example story arc: maybe one family member of one of the characters has gone mysteriously missing. Later on it's revealed they're the evil lich who is controlling the giant. Another character had their home destroyed by the giant and another character is trying to find a cure for their parents who have started to act strange (possessed by other evil liches), and so on and so on.

I have no idea if you started yet or not, I acknowledge this is a late reply. 

Alright, it honestly depends. Using some start quests to fish out what they like is perceptive and thoughtful, but it's the equivalent of going to a buffets and returning to the table with 3 dishes in hand. Don't get me wrong, the approach can help, but it will only tell you so much. You have a very small sample for them to form their opinion. Usually I'd recommend just starting with a BBEG in mind and use your first few session to establish the theme, the plot, the threat, and the tone of the game. You can withhold the BBEG for some time and allude to the mysterious BBEG here and there for the first few sessions, then pull the curtains and reveal him after some good build up. During the build up, you have the time to adjust the BBEG and expound on his nefarious deeds. I tend to have my own BBEG described enough to give an idea of what he is about while leaving the descriptions vague enough to adjust the picture as I please to better suit a big idea I have for the campaign. 

That's just what worked for me ofc.

Using a sports analogy.  Side quests and premade crawls can be considered as preseason scrimmages.  In the long run they do not actually count, but are nevertheless very important.

For the Party they get the cohesion and understand what is expected of them.  For the DM it is much more.  The DM learns pacing, they understand how to throttle the combat in real time to increase/decrease the pressure.  The DM learns how quick the party picks up (or doesn't) clues.  The DM can also pick up confidence that they are creating an atmosphere of fun no matter the curveballs the PC throw (intentional or not).   

An unintentional curveball(in a preset crawl)  was two PCs in a role playing scenario both rolled natural 20s.  The intent (written scenario) was to just set a high DC have a few words, then combat, instead those 20s created a whole new dynamic through dialogue.  The DM even acknowledged he need a few minutes to rethink the set up.   The DM was experienced, and had the confidence to adapt and go beyond the premade blurb.  A relativity new DM with a couple of previous pre written modules/side quests may not have been able to adapt on the fly like that.

If a relatively new DM feels confident that they can go to the next step with their homebrew,  one more final run of a side quest can be a good test.