What follows is a description of what I feel is are best practices for scene play that I've come up with over a lot of use (mostly in an IRC chat online environment). I don't aways manage to follow these notions as well as I'd like, but they are what I aspire to. I've presented this as a step-by-step process. This may seem complicated, but in actual use, it goes very quickly and is easier to stick to than it might appear.
As a scene ends, come up with what you think is likely the most interesting thing to do for the next scene.
If you have a good idea, go to step 2.
If you can't think of anything, or your ideas are somewhat vague or don't strike you as being interesting to everyone for sure, skip to Step 3.
Decide if the scene you've come up with is absolutely necessary to do next. There are two perspectives on when it's true that the scene you've come up with is necessary. First, there may be things that the players do not know that make it incumbent upon you as GM to force the next scene to be X. If left to their own devices, they'll come up with a scene that moves past an event that seems likely to happen from your persepective as the GM with information they don't have. Secondly, sometimes you just want to suprise the players with something that you think would be fun to do right now. Normally I'm all for play being mostly collaborative, but it's also good GMing to force scenes to happen in order to throw something new at the players.
If you decide it's time for your scene, for certain, start it, and the process is over.
If you're pretty sure that your scene is a good idea, but want to check in, go to step 4.
If you decide that there definitely may be other things that can happen before you throw your scene out there, go to step 3.
Ask the players, “Do any of you have a scene that you think should happen next?” If you're into trying to get the players to think like the characters, ask instead, “What do you do?”
If one player has an idea, usually it's the best idea to go with that, because it encourages players to make these sorts of decisions. Often it's the same thing you were thinking, and that just confirms that everyone is on the right track together. But even if different, defer to the player, or work with them to figure out the best idea and play that out.
If two or more players have ideas, then everybody should discuss until there's a pretty clear consensus on what scene to do next. Often times players may have ideas that send characters off in different directions at the same time. In these cases, you can often choose arbitrarily which scene to do first (or in the case of IRC, we'll often do them simultaneously in two different chat rooms). But sometimes there are subtle thematic bits that may make more sense resolving in a particular order. So keep this in mind when you're thinking which to play out first.
If you don't have an idea, and the players don't go back to step 1.
If the players don't have any ideas, go to step 4.
Bring up your idea and say, “Do you want the characters to X?” It's key to understand that some potential scenes may not really be interesting to actually play out.
If the answer is no that the players feel that this is not something that the characters would go about doing, or just wouldn't be interesting to have happen, then you just move on, and the events do not occur at all. Go back to step 1.
If the answer is yes they want to have their characters do X or have X happen to them, go to step 5.
Consider whether or not the scene needs to be played out.
If you're sure it needs to be played out, play it out and the process is over.
If you're not sure, then ask, “Do you want to play that out, or just say it happens?” When playing using scene play methods, this technique gets overlooked a LOT. The assumption often times in such play is that you ought to establish everything that happens using in-character narration, that this is a superior form of play or something (often a reaction from play where pretty much everything is established using OOC methods). But playing out scenes that don't have any potential for drama is not a great idea. Establish facts quickly and move on to the interesting stuff.
If they say yes, that they want to play out the scene, play it out and the process is over.
If they say no they don't want to play it out (but still want it to have happened), establish the event OOC, and go back to step 1.