The following are less "rules" and more ways I try to keep the game moving.
In general, any skill checks rolled will last for the duration of a scene. If you roll a Stealth check to sneak into a castle, you won't need to roll again for each group of guards you pass; unless there's some drastic change in the situation, if you succeed, you won't need to roll Stealth again, and if you fail, you won't be able to roll Stealth again.
The main exception is combat, where things will continue to function rules-as-written; if you're on a cliff face, you need to roll a new Athletics check each time you want to move, etc.
I will usually be telling you the DCs to things ahead of time, as well as including the defensive stats/HP of enemies during combat. This helps speed up combat a bit, and lets you work success/failure into your posts. I don't expect you to pretend you don't know these things, we're just assuming it's somehow obvious in-universe: if an enemy has a Reflex defense too high for you to hit and so you choose to target their Fortitude defense, that's not metagaming, that's your character recognizing they're unlikely to hit with standard attacks.
However! This does go both ways. In exchange for giving you this information, I will be assuming enemies (especially Intelligent ones) can see the same info about you, and they may well make use of it themselves. So don't be surprised if enemies tend to prioritize the lowest defenses of the group, or target whoever has the lowest HP.
This is play-by-post; if everybody left room for everybody else to react anywhere they might possibly react, we could spend weeks or even months on a single conversation. As such, if I feel like I have a good handle on what your characters are going to do in a given circumstance, I may just say "You all do X" to keep things moving. Occasionally I may do that even if I'm not sure it's what your characters would do, if the choice is of little consequence ("You decide to wear blue uniforms instead of red and leave the changing room.").
For your part, I'd like it if you could at least try to go along with these assumptions. Not asking you to do anything that you feel is drastically out of character - if your character would, for whatever reason, never get caught dead in a blue uniform, feel free to note that somewhere and I'll likely retcon it or something. But if there's a world in which your character would wear blue, then I'd just request that you interpret things according to that world, even if, were it all roleplayed out, your character would have been arguing for red. Just help keep the game moving forward.
As a specifically noteworthy subset of assumptions I'll make: if a fight (or other situation, but fights are the most obvious) is clearly trending towards a certain result but is going to take a while to get there, I may just declare the fight over and that result as having been reached. Depending on how certain things looked, I'll sometimes give the group one last decision or roll to sum things up, but otherwise it'll just happen.
For example, the party ambushes a group of a dozen stormtroopers and quickly takes out all but two of them. The remaining two, however, flee, and the party is struggling to catch them. Rather than keep things going round-by-round with everyone continuing the chase until someone gets lucky or unlucky enough to end things, I'll give the group one last roll to try to catch up; on a success, I'll just say you beat the stormtroopers, and on a failure, I'll just say they got away.
Similarly, though, if you're the ones getting ambushed and the fight is heavily against you, I may just declare that you've lost and been captured, no rolls, no nothing. I won't do this if you aren't clearly losing, and I'll usually warn you before I do, so I don't expect any pushback. Especially if I decide things against you, it'd be reasonable if you're a little upset, but please try to understand why it's happening and that the point is to keep the game moving so that you can recover and come back stronger. I'm not doing this to make you lose, I'm doing it because I was sure you were going to lose and I wanted to rip the band-aid off.
It is worth noting I won't use this rule unless I think things are going to take an unnecessarily long time, and I won't use it for any particularly dramatic encounters - if you're fighting the BBEG, we'll roll everything out even if that means a solid week of trading rounds of attack/block/miss. I will also never kill you this way - if your life is on the line, you'll get to fight to the bitter end.
(Despite this massive, several-paragraph wall of text explaining myself, I really don't expect this to happen much, if ever - I just don't want it to be surprising and controversial if it does.)