It would seem that for simplicity purposes the best ones to go for are the smaller amount 'free bets'. For example, when i opened my
ladbrokes account they gave me a £20 free bet. You only needed to wager it once, granted you only got to keep the winnings, but the chance of losing was offset by laying on
betfair. Ok you only make like £20ish, but thats not bad for 5 mins work. And if you can find 50+ bookies that are offering the same 'free bet', well, its worth doing.