You'll need to bid really low and over deliver on your initial projects to build up good feedback . . . it's tough getting projects if you don't have at least a few 5 star reviews.
Write a custom proposal tailored to the client and their project . . . outline similar work, suggestions to make the project a success . . . or improve on what they have in mind . . .
If it's something simple think about setting up a quick mock up, sample or demo.
Most importantly try to connect with them, get them to message you, ask them a couple smart questions that will most likely get them to message with you. Once you are messaging with them you can answer questions they might have, follow up with them, point them to demos/samples. Once you're communicating with them you have a good chance of winning the project.
Consider creating a video to link to in your proposal that outlines who you are, how you work, and your thoughts on their project and related experience.
The online sites are dominated by low fee offshore guys so you could tout your location, if you are not in that location and that all work is done by in house. Some US clients prefer US based . . . buy american, more secure, first language, etc.
I know this is only 'beta customers' but you need to focus on developing your own clients . . . your fees will be 2x to 4x vs. the typical work you find on the job boards and clients will be better too. (typically speaking, you will get nice gigs and clients occasionally, but the avg. is lower fees and lower quality clients).
Plus the rating system is super important for getting work and occasionally you'll get a client who either rates you 1 star because they are unhappy with your work or something totally unrelated to the project or they just don't understand the importance of 5 stars and rate you at 3 or 4 even if you do a great job. So that's a constant worry/battle to keep as close to 5 stars as possible.
If you haven't already . . . read everything you can from Patio11 and Brennan Dunn . . .and check out their podcasts.
Lots of good info on getting quality clients and doubling your freelancing rate . . .
Good luck . . .