[dsirijus]

It is pretty simple:

1. Determine how much time are you willing to allocate for work.

2. Set whatever the price that will fill up that time with client work.

3. Once you have more clients than allocated time, increase your price.

(bonus) 4. Client pool and time permitting, target projects that will further evolution/creation of skills you want to improve/develop, not the ones that you've already good enough at.

To be able to do that, you should have some form of rudimentary tracking of your time/price/value performance. No need for overkill here, a simple regulary updated spreadsheet or even just a text file will do. The accent is on "regulary updated".