We've writen a post over on the IntuitionHQ blog with 10 Quick Usability Testing Tips. You can head over there for the full post, but here is a brief summary:

1. It's always a good time to test: No matter what stage you are in the process, test.
2. Test early and test often: You get the best, most effective results if you test early and test often.
3. Don't be afraid to get your ideas out there: Many people are afraid of sharing their new ideas. Don't be. People will be supportive.
4. Use everyone at your disposal: Ask your friends and family to help. Ask strangers in the street what they think. Ask everyone.
5. Don't listen to the naysayers: Don't despise if you get some negative feedback - testing helps make it better
6. Experiment with the questions you ask: Try a few different styles to see what works best for you and your site
7. Use social media: Twitter and Facebook are great resources for recruiting new users. Use them.
8. The web is full of helpful communities: Find relevant forums to share your tests and get great feedback
9. Learn from your results: Once you've done your testing, study your results and make changes.
10. Do it now: Don't think, 'Hey, that's a good idea - I'll do that in a month or two' - do it now.

Hopefully these tips are handy for you - be sure to let us know if you've got any questions.

Happy testing!