2. Direct contact, especially if you see the domain is either parked or is sitting fallow.
Do a lot of research on your traffic domain. There are plenty of traffic scams used to inflate numbers.
Look to pay 5-10Xs the domains proven revenue. Traffic domains ain't cheap and they ain't gettin' any cheaper as time passes.
Do a lot of reading at the domain websites before you attempt to enter the game. Go back into the threads a year or so to flesh out price patterns, issues, etc.