If you are given a choice of topics, think about what topics interest you that meet the criteria for the assignment. Jot down some ideas before you commit to extensive writing. Think of 3 or 4 possible topics which might fulfill the purposes of the assignment.

Use some brainstorming techniques:

• Free write ideas without censoring them. 
• Make a list of ideas.
• Create an outline.
• Draw a large circle (your main topic), then spokes labeled with the names of your sub topics
• Draw a tree (your main topic) with branches labeled with your sub topics. 

After you narrow down the  possible topics, try to prioritize them. Which topic might best fulfill the assignment?  From which topic would you learn the most? Who will be your audience?  How will your audience benefit from  learning more about this topic? Then narrow down to first choice, second choice, and so on.

If this is a research writing assignment, begin your research. Review research strategies. About which topic were you able to find the most credible sources?  What are your guidelines for evaluating the credibility of your sources for this assignment? The quality of your sources is a big factor in the quality of a research paper. 

After you gather preliminary information and become familiar with it, do some free writing. For example, you could try to construct a preliminary thesis statement and jot down some main points you might cover. Frequently, when writers have trouble developing their papers, it is because they didn't begin with enough ideas. Creating a fund of ideas from which to draw is important in this stage of pre-drafting. Don't worry about correct sentences at this point. Just get some ideas down to help you get situated in your subject.

Start narrowing down your thesis (your controlling idea).