- Sample size: Just five people can be a large enough number of users to find common problems in your layouts and navigation (see Jakob Nielsen’s article on why using a small sample size is sufficient).
- Choosing your testers: A range of different technical ability can be useful, but be sure to only focus on trends—for example, if more than 50% of your testers have the same usability issue, it’s likely a real problem—rather than individual issues encountered.
- Testing location: If possible, visit the user in their home and watch how they use the site—observe how he/she normally navigates the web when relaxed and in their natural environment. Remote testing is also a possibility if you can’t make it in person—we’ve heard that Google+ hangouts can be used effectively for this.
- How to test: Based on your site’s goals, define 4 or 5 simple tasks to do on your website, and let the user try to complete the tasks. Ask your testers to speak aloud so you can better understand their experiences and thought processes.
- What to test: Basic prototypes in clickable image or document format (for example, PDF) or HTML can be used to test the basic interactions, without having to build out a full site for testing. This way, you can test out different options for navigation and layouts to see how they perform before implementing them.
- What not to test: Focus on functionality rather than graphic design elements; viewpoints are often subjective. You would only get useful feedback on design from quantitative testing with large (200+) numbers of users (unless, for example, the colors you use on your site make the content unreadable, which would be good feedback!). One format for getting some useful feedback on the design can be to offer 5-6 descriptive keywords and ask your user to choose the most representative ones.
Read full article here http://googlewebmastercentral.blogspot.com/2011/12/website-user-research-and-testing-on.html