Process in selecting good sources:
The process you use in selecting sources to support your thesis is when you are choosing high reliable sources. For example sources that end with
-.org
-.net
-.edu
-.gov
-in some cases, .com
Make sure you select them by reading the title. (the title should give an idea of what the document would be about)
If you see bad words in the site that automatically mean NO!
Don't forget that the site should be about your thesis. If you are searching for a long time and can't seem to find any than ask your teacher! Your teacher probably knows many good sites to go on and there is no harm in asking.