There are a number of decent checklists that have been developed to help you evaluate websites. One of these checklists, the CRAAP Test, was developed by Meriam Library (California State University, Chico). It delivers a list of questions to help you evaluate the information you find.
For a useful CRAAP worksheet, refer to the rubric (pdf included below) developed by Central Library MCHS. It prompts you to grade a website on each of the CRAAP criteria and will result in a final score that could range between a potentially "highly questionable source" to a "excellent source for research."