every now and then I'll go through the mse competitions forum for the ones finishing on the next day, will enter all the ones I like the look of/can be bothered with, it's surprising how quickly you realise a phone you're probably only going to sell on isn't worth upto 3 mins of your time to enter.
To date I have won:
-an electric toothbrush from an argos competition
-a free ski lesson and meeting the jr gb ski team (gave to my boss' kids)
-a free meal at grill on the alley in manchester
obviously you stand a better chance on the more local ones, I'm fairly sure I must have been one of the only entrants for the ski one, because after I entered I noticed the max age was 16 or something, and I'd put my age in the entry form and still won.