It should be worded in the form of a question (including a question mark). Although the question will never actually appear in your paper, your paper will be the answer to the question.
The question should be appropriately narrow for a college level research paper. An entire book on a topic means it is too broad. Look at chapters within a book on your topic. Chapters tend to look at a narrower aspect within the topic and may provide you with ideas for narrowing your topic.
The question should be clearly worded and grammatically correct.
The question should be open-ended and express no bias. The expectation is that you are researching the topic without bias and your conclusion will be based on the research that you find.
The question should be academically challenging, allows you to take a stance, make a judgment based on analysis of research, and allows you to bring insight to the question.
The question should be grounded and be based on evidence rather than beliefs.

Coming up with a solid research question can be challenging but it will save you time, keep you on topic and lead to a stronger final paper.