Once you have a sense of your overall direction, you need to narrow it down to a specific topic.
Use your research topic or question to identify the main ideas, which will become your keywords.
As you continue searching, refine your search by adding or combining different keywords that further explore your topic. You may find you need to modify your topic.
This is where your mind map comes in handy! Where do you have the greatest concentration of notes? What connections have you made between ideas that suggest an interesting relationship?
Your thesis is the short answer to your research question (the rest of your paper or presentation is the long answer). It should be the last sentence of your introduction paragraph, traditionally. Thesis statements should be:
If I’m writing a paper about cookies, my thesis statement might be:
Oatmeal raisin cookies are the best flavor due to their relatively healthful ingredients, chewy texture, and the ease of their creation which means they’re consistently yummy no matter where you get them from.
Silly topic and casual language… but if you read that at the start of the paper, you’d know right away: 1) I’m talking cookies, 2) I’m discussing oatmeal raisin cookies, 3) I think those are the best flavor, and 4) I have those 3 reasons for saying so, that I’m going to spend the paper telling you more about. (And on that last point, notice I don’t have to get into any personal I or we pronouns – it’s implied that I'm talking and these are my conclusions.)