Second, choose the right freelance marketplace which are not scams because there are hell lot of scams are running out there. For this particular point, I would like to share my good and bad experiences with you:

www.Elance.com (Highly Recommended)
www.FreelancerCircle.com (Highly Recommended)
www.Upwork.com (Highly Recommended)

www.PeoplePerHour.com (Optionally Recommended)
www.Guru.com (Optionally Recommended)
www.WorkNHire.com (Optionally Recommended)

www.Freelancer.com (Not Recommended)
www.Outsource.com (Not Recommended)
www.RentACoder.com (Not Recommended) 

If you are looking for Micro Freelancing, go with the following sites:

www.Fiverr.com (Highly Recommended)
www.Freecie.com (Highly Recommended)

www.Freecie.com is currently open for skill / talent sellers so it would be right time to get in.