[mootothemax]

Get paid some percentage up front

To add to this, I would ask new clients for a few days pay up-front as a sign of good faith.

There were several clients who ran away, absolutely outraged, they'd never heard of anyone asking something so ridiculous in all their life!

Running away screaming was very rare though, and by some good fortune, all of my regular clients were an utter delight to work with.

Stick to your guns though: get paid up-front, and invoice as often as you can. (Weekly in my case).

Offering clients a small discount for paying for a good chunk amount of development time in advance also worked well for me. (Lowest I'd typically go was 2 months with a 5% discount).