I've spent more time on advanced world gen than I'd like to admit, and used to have extremely specific and kind of frivolous preferences(x amount of mountain regions, y amount of desert squares, must begin generation under the light of a full moon, etc.). Eventually, I adopted a "whatever, roll with it" mentality and I've been happier ever since. I still have my preferences, but these days I focus more on broad strokes rather than fine details, and I have a lot less map rejections to deal with as a result.
I try to stick to setting x and y variances slightly above default, but I do set a desired number of regions for mountains, forests, and plains. I only do this to ensure at least one of each civilization spawn, so I disable the rest. I also narrow the temperature range to 32-64 like I always have, but I think that became redundant after I stopped generating worlds with poles.
The only big thing after that is a little eccentric. I always change nearly every numerical value to a multiple of eight. End year, megabeasts, rivers, pretty much everything except meshes, cavern settings and cave depth. I don't remember when or exactly why I started doing this, and the only reason I keep doing it is because I haven't found a reason to stop.
Edit: There's actually one other thing I've made a habit of. Once I start generating a world, I always, always, always immediately return to the menu and switch 'use seed' to yes before proceeding. If it's set to random, that parameter is cleared after world gen is finished, and the only way to get that seed back is to export the info. If the game crashes during world gen and you didn't save the seed, you're SOL. I've had a lot of promising worlds vanish into the mists due to this, and I've gotten so used to doing it that I actually forgot to mention it at first.