don't use the address of somebody you know. they may want to sign up at some point in the future and then you'll have to "move" away from their location (assuming you know ahead of time that they want to sign up).
a completely fake address is the way to go. i always just add a bogus apartment number to a fast food establishment.
ahhh ok, i used my local informant to find a real apartment complex.. and list an apartment number 9 floors above the top of the building. Shhhhhhhh