To become a successful affiliate then you must work hard, there is no easy way to generate large revenues. If at first it doesn't succeed then don't give up often small changes will change.
Things to remember:
-Business is seasonal. For example if you promote flowers then you going to see bigger sales and better conversions around Valentines Day, Mothers Day and Christmas.
-Problems will happen, merchants sites break, tracking issues, conversions drop etc. Try and stay as professional as possible.
-If something isn't going well talk to the merchants and the networks. They will be in the best position to help you maximise your return.