As you think through your topic and do your general or background reading, make notes about how your thoughts associated to the topic could be developed. For example, the English 110 assignment on power in Antony and Cleopatra might evolve by:
Noting the Oxford English Dictionary's definition of power:
"ability to affect...a person or thing; a particular faculty of mind or body; ability to affect something strongly; physical or mental strength;might;vigour, energy, force of character...; political or national strength possession of control or command...". Depending upon the type of power being employed, "use" or "abuse" can be either seen as matters for personal or public opinion based upon whatever perspective is being employed.
Re-reading the play:
Look for scenes, characters, activity, staging and quotes which characterize the above definitions. Each incident could be noted on a 3x5 card, and grouped under a particular definition with your own comments on how the incident might be used in your paper.
Reading supporting material:
Read materials derived from your research in the same manner, using note cards to link relevant passages from supporting material to incidents in the play and also to the definitions.
These notes or cards can be used as various elements of the paper are prepared. They can help organize concepts from definitions and incidents within the play, as well as link these concepts to opinions or quotes from supporting research. Eventually, these same cards can be used for your footnotes or bibliography.
Narrow topic and come up with a thesis
A thesis statement should express your goals in writing the paper - how you interpret the assignment, what you think the major issues are, how you are going to proceed and what you expect to end up with at the end of the paper. Your thesis is NOT a restatement of the assignment as given. It is what you think is important about the assignment.
Example: You may wish to discuss power in the Shakespearean play Antony and Cleopatra from the perspective of Cleopatra as Queen of Egypt and Antony as an overlord representing Roman imperial interests - looking at the power of states rather than personal or sexual power. This narrows the topic to something more manageable.