I worked on freelancer.com for a few weeks, before getting a job at an investment bank.
During that time, I got a few jobs coming through, and found a regular client.
My approach was:
- don't put the lowest bid: actually people will assume that the low bids are from inexperienced people. Put a reasonable sounding bid, and write a concise bid text, in fluent English, that shows you know about the subject and have read the client's requirements. Ask them questions to clarify points, again showing you read the original text the client wrote
- pick some very narrow field you're really interested in, and that there seems to be a market for, and be really good at that, and market yourself as a specialist in that field. There will be fewer potential jobs arriving, but the chances of being picked for one are I feel much higher, and it's much more satisfying to just submit a handful of bids and get a job, than spend a whole day spraying bids everywhere, and getting nothing.