I have some experiences on freelance jobs and I think it could be valuable for someone. First point is: be organized, work as freela it’s about work with time, that time must exist and you have to use it with conscience. Another important point is the quality of your work, the next job may depend on your previous work, as they say: “A good company, I recommend to ten, a bad company I tell for everybody.”
Keep in mind that many people will come looking for a different set of tasks: final project at college, college’s work, work for research institutes, companies facing difficulties in terms of technology or other reasons and the list goes on. Pricing and know how to choose which project to accept is crucial. There is no rule (silver bullet) for you to make the right value for that project. Unfortunately the (exact science of) mathematics does not have this function yet for me. This will be achieved with time and experience (but, please don’t sell yourself for ten dollars, value your work). Also there is no practical rule for you to notice how reliable or good will be a customer, in general observe his problem, his motivations that led him to seek you, see how much conscious about the support post-work he is… I never did a freelance job and have not received the money. It’s very important to make a law contract and make it valid to each client.
So if you could give one tip is to organize and do a great job. Don’t accept work that you won’t get done, just because it may look very profitable. Since some customers will ask you for a NASA rocket for two days, learn to say I can’t. (in that conditions) Always try to watch the feedback of your work and try to improve it.
PS: You will not only acts as a Developer / Designer / Supporter , you will also act as a Consultant and Administrator as well.