I have two different definitions of a "successful" handicapper depending on one's point of view, and they are not mutually exclusive.
There are a FEW exceptions and I mean FEW exceptions:
1) A capper who has the gift of gab, lies, spin and overall deception in convincing a number of people to buy their picks no matter how good or bad they are.
2) A capper who over time(weeks, months and years) who loses(not wins) a client's money/bankroll the SLOWEST and thus provides them with entertainment
for a longer period of time than other ones who bury their clients a lot quicker.
This is my honest belief based on following these operations since they started in the mid to late 70's.