Start iChat without logging into accounts
If you use iChat (or Adium—this hint works for that program as well) and have multiple accounts, there may be times when you want to log in to one account, but not the rest. Most of the time, though, you log in to all your accounts—so you’ve left the “automatically log in” setting enabled on each of your accounts. As an example, you may have a work account and a personal account, and would rather not log into the work account on the weekends. You could change the setting in iChat’s preferences, but that’s hardly an ideal solution.
You could also manually log out of each account you’d rather not be logged into, but this is a bit of a pain—and it will ‘flash’ your availability to everyone on your buddy list before you log out. Instead, try this alternative. Start iChat (or Adium) while holding down the Shift key. When iChat (or Adium) launches, none of your accounts will be logged in; you can then manually log in to only those accounts you’d like to activate.
While this may not seem any simpler than starting with all accounts logged in and logging out of those you don’t want, this method saves a needless login—and insures you won’t accidentally leave an account in a logged in state.