You evaluate information all the time by asking questions such as...
Do I really need this information?
Who am I receiving it from?
Is it a reliable source?
Is there a bias?
Based on the answers, you decide if the information is reliable or not.
You should think critically about any information you receive.
This includes books, articles, websites, etc. Even information from professors and other professionals.
There are a number of criteria to take into consideration as you evaluate resources.
Purpose - Why was this item written?
Authority - Who wrote it, what are their credentials?
Currency - When was the item written, does currency matter? It may not depending on your topic.
Accuracy - This can be hard if you don't know much about the topic. Generally books and articles go through some type of editorial process. Does the resource have references you could check?
Relevance or content - Does the resource address your topic question?
Audience - Who is the intended audience?
You can use the same criteria for evaluating information on the web. In addition, there are some specific things you can look for.
Look at the end of the url (uniform resource locator) Is it .org, .com, .edu or .gov?
.org - nonprofit organizations
.com - commercial/business
.edu - university or college
.gov - government site
Look for an "About Us" link or something similar. This often gives you information about the website.