use the link at my signature to get my personal strategy. It's very effective and very user friendly, too.
Advanced Block MOD (with topical DNSBLS list) + user activation = User
not any other Anti-SPAM MODs
=> very, very rare (one in two or three months) successfull SPAM registrations, they seem to be new or human SPAMMERs
Optional or for the future then SPAMMERs will take the UTC-12 trick (Most of them still don't. ):
ADAP 1.4.x with account activation = User+Admin (Double Activation) + Auto user prunning
=> some rare successful registrations
=> Double Activation (User+Admin) helps you to identify them as SPAMMERs and makes it easy to delete them. The accounts with real email address and auto account activation responses will not be activated automatically like it is with account activation = User.
=> Auto user prunning deletes the rest of them, doesn't matter if activated ot not activated