The Basic Process
Step 1
GM gauges what the players want and describes the scene. As it's being written, players can continue to make suggestions.
This step is when the GM prepares and reads (or otherwise disseminates) the "read aloud" text describing the outcome of the previous scene and the approach of the next one.
In-session:
Players get to hear the text as it's written and have the opportunity to add details, producing a more collaborative story.
Web Application:
Players have a variety of communication preferences regarding how they want to be contacted when the GM posts the next scene, such as email or SMS (most cell companies have an email address for your phone which they forward to you via SMS). In addition, players might have the opportunity to line-item veto certain sentences, especially if they relate directly to what their character would do. The GM may decide that some of the players will need to approve of what's been written before moving on to Step 2.
Over email:
Players receive the next scene via email. Because the GM lacks effective feedback while writing, the GM may have to take certain liberties, especially when describing player character speech and behavior. Alternatively, two or more scenes can be described and voted on, so players at least have some clumsy control of plot direction.
Step 2
Players suggest any tactics that the group might take or that other players might want to consider.
This step is when players can just blurt out ideas whether it's most appropriate for their character or not. This step comes with the risk of players unable to decide a next course of action, either because they aren't reaching the conclusions the GM hoped they would or because players disagree with what to do next. While it can be perfectly fine for characters to temporarily separate at times, it's important that each player feels their own story is being told and that they can express and explore their own play-style.
In-session:
This step goes faster in person. However, group dynamics could overshadow the potential contributions of quiet, shy, and contemplative players.
Web Application:
Players can chat their ideas along with other information, such as why they would like to see their idea be used. For instance, to further develop a particular character story or to help justify a deliberate shift of a player character's personality traits. This helps the GM to best determine which idea delivers the best balance of entertainment.
Over email:
Since discussion and development of ideas is difficult using email, it might be better for players to immediately roll initiative (re-rolling it each round) and skip straight to Step 4. Time limits justify the GM guessing the actions of a player character to keep the plot going. For instance, if a player doesn't respond to a scene description within 24 hours of it being received.
The web application especially could allow easily understood time limits and notifications.
Step 3
GM decides the group's general course of action if players don't reach a timely consensus.
In-session:
In-game, it's very easy for the GM to encourage good ideas. And it's just as easy to point out your favorite idea as a way of helping the players focus.
Web Application:
Using an application, sophisticated methods can be used. Ideas can be submitted so that they're more than chat text. Once listed, they can be ranked or vote on. Split votes and divided passions can be decided by the GM or by letting the application randomly select one.
Over email:
If the GM feels there's no consensus or no viable idea, the GM can dole out hints or suggest ideas. However, the GM should allow for discussion to occur because as long as it's entertaining, that's the point! And the GM should try to encourage the players to develop their own stories instead of just relying on the GM's vision.
Step 4
Players state their actions and make their rolls.
In-session:
As normal, players state their intent and roll dice to determine if they were successful. Outside of combat, the GM might want to ask for everyone's intent before anyone rolls, even if you are using initiative. The reason for this is that during combat, generally all the players are on the same page. Social situations and opportunities involving story are more subtle, and it's rewarding to coax those subtleties into the play-style.
Web Application:
Players can choose to roll themselves or let the system roll for them. This is especially useful if some players can't interact as much, yet their characters need to make rolls. Also, submitted rolls can be tallied, and statistical anomalies can be corrected as bonuses or penalties on the GM's rolls against that character.
Over email:
Over email, the GM might want to consider asking for everyone's intent before anyone sends in their rolls. Since there's no map (probably), this helps the players and the GM imagine where all the characters are, especially if players want to change their mind based on the success or failure of another player character's actions. You don't want players to wait until their initiative before sending an email with their action and roll; that would take forever. What you don't want is players sending in skill checks for conflicting actions, leading to players wanting to change their action after they've rolled. Knowing the character's original intent, the GM can judge if a player character can change their action and how effective that action might be.