Here are 4 vital tips that work for me
1) Always get a list of potential buyers before buying a name
2) Don't park a name and wait for a buyer, actively approach end-users
3) Don't buy loads of names, buy 2 or 3, sell them and then reinvest that cash, if you dont, renewals fees will eat any profit you make.
4) Don't not hand-reg crap names (no good names left) , buy good names off existing owners and resell them, quality over quantity is crucial, have 2 decent names rathern thatn 20 crap names you'll never sell.