Good questions!
This is the first time doing a Play By Post for me too, so I can't say for sure. However, I plan to do the following:
1. Relatively strict adherence to whatever schedule is decided upon. As said, I anticipate this being no more than 2 'story' decision points per week. I will endeavor to have the decision points occur on set evenings (for instance, Friday and Tuesday - chosen at random for the purposes of this discussion; I'll probably poll people soon when they'd prefer the decision points to be if they have a strong preference). People will have two days to provide their input. If after those 2 days (so for instance, Monday and Friday), they haven't responded, I'll make a decision for their character based on what I've seen so far. In general that probably means they'll go along with whatever the majority has decided and it'll be assumed that they didn't have much of a reaction one way or another. If it's a decision that could be swayed by a character's IC knowledge, I will take over the character as an NPC for the purposes of that decision point, attempting to keep the character true to how it was played up to that point. An important point to note here is that if you have information you want to keep secret, you should tell me this, otherwise I could very well spill the beans on it if the knowledge could be useful to the party in some fashion. (This will be repeated in a more formal 'How we will do things' post before we get started).
2. Combat will be done differently. People will be expected to give me a brief summary of how their character generally will approach combat. Something as simple as: "Hide first, shoot arrows second, attack with axe third, run away if I've taken more than 50% damage." If combat occurs it will initially be treated as a normal 'story' decision point (ie, I'll endeavor to have it occur on one of the two normal days). I'll describe the initial situation, people work up a basic plan of attack (or defense, or running away) and give me as detailed instructions as they want for their character, and then I'll start running through the combat.
If I run into a situation that can't easily be resolved by the instructions given, I'll describe the combat up to that point and ask for new instructions (from the entire group, or individuals depending on the situation). This might happen before the usual 'decision point' date (ie, the first combat decision point comes on a Friday... all instructions are received before Monday so I start running the combat Sunday night... run into a situation I can't resolve and ask someone for a decision... they will have until Thursday night to respond since that's the deadline for the 2nd decision point of the week. If they respond earlier, I'll continue to resolve matters immediately, otherwise there will be a bit of a bog down.) I'm hoping combat won't bog down often, and if it does I may have to come up with something else.
Combat also might very well be partially interactive. The default will be the mode I described just now, but I may tell people that I will be running the combat on a given night. If anyone says they will be online at that time, I'll provide a round by round description and people can respond within a reasonable time (15 minutes). If there's no response I'll continue with the next round and so on until the combat is over or until I've reached a point I need more input from people on.
