Hexcrawling: The Procedure Is Not The Game
A short one, and obvious to most I'm sure.
It can be difficult, I think, to know when to break the rules when you're playing a new system. What rolls are important and which can be ignored? Which ones are tied to another subsystem that will fall apart without them? It takes time running a game before you get a clear sense of these things.
As I play more hexcrawls I am learning that the overland travel procedures are useful a lot of the time, but they get in the way surprisingly often! My initial inclination to stick doggedly to The Procedure payed off... maybe a little over half of the time?? But often I found that I was struggling to fit the players' intentions into the input slot of my little travel mechanic. Sometimes it simply did not fit, and the players' intentions got mangled in the process.
My travel rules use four-hour time blocks, and 6km hexes. There are rules for getting lost, rules for random encounters, rules for foraging. But there aren't rules for spending one single hour chillin' before moving again, effectively breaking the time scheme. There aren't rules for traveling in increments of 100m instead of 6km. I could add them, but I can't cover every corner case. Even if I could, it would stop being abstract enough to be useful.
At a certain point, no matter how flexible the rules are, your players will approach a situation in some fashion The Procedure can't handle, and in those moments I am learning that The Procedure isn't the game. The Storytelling is the game (I'll stop with the obnoxious capitalization now, a post this short can't support it). The procedure is just a tool to help figure out the storytelling, and it's not always the right one, no matter how well designed. Sometimes you're better off inventing another rule that suits the circumstance and feels in keeping with the spirit of the mechanics. Tabletop is improv and sometimes you gotta improv some rules, too.
Consistency is key. Players want to know that things will be resolved the same way every time so they can make good choices. It's maybe worth noting down how you handled a bespoke scenario so that you can handle it the same way next time, although hopefully your approach and understanding of the rules will result in the same handling every time.