so, whats your guys' rules for when i player is gonna be absent?
our newest addition had let me know before committing to the group and weekly game that he was going out of state to see family for 2 weeks, hence missing 2 games. those weeks are coming up soon.
he already had suggested i just playing his character as the DM. i think that would be fine as i already know his character pretty well having played with him a few times before this in my first group.
what do you guys do?
It can be a tricky situation. For me it depends on how well I know the player and the others at the table. If at all reasonable I would find a in the plot rational for them to be missing for that session, although that can create problems also if you have encounters balanced for a certain amount and variety of people and then have to change everything to fit the party you have. I don't deny them XP though for missing a session. For me it's just too much hassle to figure out and keep track of when players have differing amounts, and it's just easier. If something happens and missing sessions becomes a chronic problem for a player then I would either expel that person from the group or try to make it where a certain spot in the group could potentially be a revolving character spot for whomever wanted to show up that night and got first dibs on it.
In situations where it's not plausible within the plot to have a character suddenly go missing or they will play a key element in the upcoming session, and the missing player doesn't mind, then I would either (in descending order of preference):
1. Let the rest of the players decide collectively what that character does and control them by a quick vote, unless the missing player has a chosen designate player he wants to control his character.
2. Let a single other player play the character of the missing player.
3. Play that character myself.
If I can help it I, as the DM, would rather not control a player's character like that. It can cause conflicts of interest, and make it harder to play the character how he normally would because I would feel that I would have to be either very generic in what I did with that character or very conservative and careful or both even if that's not what I think that player would have done. It doesn't help at all that I know what going to come up for them and what challenges they face before the players do either.
Part of the problem is that if everything goes fine then maybe nothing ever because an issue with it for that session, but lets say the character of the missing player gets killed, loses an item the missing player really liked and went to a lot of trouble to get, or something else really bad happens to that character. It's one thing for that to happen to one’s own character, but it can cause the people that were substituting to feel real bad about it. It might cause friction for the player that was missing to have that happen when he wasn't there, even if the people or person controlling his character really did do they best they could and tried to make the decisions the missing player would have. For it to happen there needs to be a lot of trust and understanding between everybody. In a lot of close groups in can work well enough though.
That's also why I especially dislike doing it as the DM. For example, if there is a nasty trap up ahead, and I know the character of the missing player would often go first into it then it creates a problem when I don't want to screw up somebody's character for them or worse yet make it seem like I purposely lead the missing player's character into it for other than role playing reasons. That's where the conflict of interest can come in.
There is also another option, even if in world their absence wouldn't be able to be easily explained, especially if the character isn't vital in the upcoming session. That is to have all the players just use extreme suspension of disbelief for the convenience of working around a missing player, and just have everybody in the game including all NPCs fail to acknowledge the absence whatsoever of that character for that session. That character just pops out for that session and pops back in to be with everybody else when he returns. It's not even as much as they are pretending he's not there as it is for all purposes for that session as he doesn't exist until his player returns. It's definitely not the most realistic in world solution, but sometimes it can be the most practical real life one if people are willing to buy it for the sake of simplicity and not wanting to do potential damage to character.