The types of resources you plan to research and include as part of your thesis can influence your search strategies.
Think about the type of material that you need -- do you need to find a letter? A scholarly article? A book?
Scenario 1: You found a letter written by William Blake and would like to find information that situates the content of the letter in the context of Blake's work. What type of resource might you look for?
Scenario 2: You are interested in movies that reflect and comment on William Blake's work. Where might you find information?
Scenario 3: You want to find an analysis of biblical influences on Charles Dickens' work. What might you search for?
Note: knowing what you need to find will help you find it. Some databases have scholarly articles, while others include popular sources. Many have both. In addition, there are databases that include illustrations, musical recordings, and more.