Absent Players
One issue that’s going to come up is how to handle experience for characters who weren’t present for a session. As with other table rules, decide on a policy and stick to it, although it’s all right to make an exception for the player who misses a lot of sessions for a good reason.
The game works better in a lot of ways if you just assume that the characters all gain experience and advance levels at the same rate, even if their players miss a session. You don’t have to worry about players lagging behind the others, and players who miss a session don’t feel like they’re less effective. D&D is a cooperative game, and it’s more fun when all the players are on a level playing field, able to make equal contributions to the group’s success. All the players can share in the excitement of gaining a level at the same time. And it makes tracking XP much easier. In fact, a group could decide to delegate the job of tracking XP to a single player, who could announce when the characters go up a level.
The alternative, of course, is to give XP only to the characters who are present and who participate in each encounter. If a character is dead while the rest of the party faces an encounter, that character doesn’t get XP for the encounter. If a player misses a session, that character doesn’t get XP for the whole session. The result is that players who never miss a session get ahead of those who miss the occasional game, and eventually they wind up a level or more ahead. There’s nothing wrong with that.