i read on a site of 4 guys who affirm that they together won over a half million dollars on online casinos some rules:

1 dont play with risky money
2 play on casinos you like. listen to your gut. dont look only for the best bonus.
3 place relativ small bets
4 dont play games you dont understand
5 play in the middle of the month and in the morning
6 quit a game after a big bonus win for a while
7 quit casino after big withdraw for a while

me personally would recommend rival and microgaming casinos - very nice slots and serious cash partners. e.g. beware of realtime casinos.

after all: dont think you can beat the casino. on the long term the casino wins! that what math say. you might get lucky sometimes. see the winnings as extra money. and if you play every month begging for you pay check you need professional help.