Begin by creating a portfolio of your work and highlighting it on your LinkedIn profile. If you don't have a portfolio of work to point to, you need to get on that ASAP. Take on interesting paid projects via elance, guru, etc. or via a local placement agency, bidding aggressively if necessary to build a portfolio of work that will become the single most important reference point of your capabilities.
Determine a technology or platform focus. It's much easier to get work (and charge more) if you've got a reputation vs. being a jack of all trades developer. Yes there's tremendous value -- once you land a project -- to a broad set of experiences, but in the sales process it creates confusion. Pick what you love and can talk passionately about. If you're on the fence between 3 technologies, pick the ones that corporations view as most in demand.
Understand your target individual (the person who signs your contract). If you can understand and communicate directly with CEOs and CFOs in terms of business outcomes you will make 2-3x more money than if you are selling technology expertise to a CTO / head of IT. Technical managers are accustomed to looking for talent they generally view programmers as higher or lower skilled replaceable components. With a CEO, you can become a trusted partner - that's often not the case with an IT manager.
Once you've done all that, begin networking. You can find projects online, you find long-term clients via relationships.