Employer Permission

When do you need employer permission? 1) BEFORE entering into any kind of competing business plan or independent contractor arrangement. 2) need both employer and 3rd party written approval to enter into a contract with a 3rd party (as an investment consultant etc) 3) what about for non-competing activities that could not possible disadvantage the firm (like a political office?) 4) what else? it seems like there are half a dozen ways this can go – anyone have any tricks to remember it?