I'll be taking a week off for vacation, how far in advance should I inform my manager about this?
As soon as you know it.
First reason, for your manager :
- It helps your manager to organize the team planning, and to know in advance when there will be few people available in the team.
Second & third reasons, for you :
If many other colleagues have scheduled holidays at the same date, it's often the "first arrived, first served" rule. Telling him asap increase your chances to have vacation the week you want to. If he wants to plan something for you (training, meeting with a client or whatever...), he can also take your request on consideration, but only if you made the request before.
If you tell him soon, he will approve your vacation soon, and so you can reserve you hotel, plane whatever at the best price.