As I've said on my free stuff page I love a competition and have been doing them online since 2003. During this time I have literally won hundreds of prizes.
At some point, when I get time, I am going to put my list of prize wins online to keep track of them and so people can see that online comps are really worth entering.
There is no science to my winning online competitions, it really is a numbers game. The more comps you enter the more chance you have of winning. If you enter enough you are guaranteed to win eventually!
As I only have up to 1 hour each day spare to enter comps, and sometimes less, I don't enter as many as I'd like. I don't bother with tiebreaker comps, even though they have less entries and therefore a better chance of winning, simply because I don't have the time. I concentrate on the easy-to-enter comps and enter as many as I can.
To find the comps I use the Prizefinder website. It is free to use and helps you keep track of your entries.
Some sites have comps running all the time and you get used to the entry requirements. Others require you to log-in, but once you have logged in you can enter each competition with only 1 click of the mouse.
I use the google toolbar Autofill facility in conjunction with Internet Explorer as I find this combination works best for quickly filling out online entry forms. For some reason Autofill does not work as well with Firefox and you can't use it with Google Chrome.
Generally I enter for prizes I want to win plus the occasional prize I think I can sell on Ebay. Although I haven't yet won a really big prize I live in hope and enjoy the feeling of winning even a small prize.
You have to look on entering competitions as a fun hobby. If I worked out the total value of prizes accumulated over the past 6 years and divided it by the number of hours I've spent entering them I don't think it would reach minimum wage! But the thrill and anticipation of a possible big prize makes up for it all.