For all practical purposes, it's useful to view a position statement as a "work-in-progress," a statement that evolves or emerges as your research progresses. It's not necessary that you begin with an ironclad position. A vague idea will do.
As you learn more about your selected-or assigned-issue, you may find your stance changing. Keep an open mind in this regard: It will help you clarify and focus your final position on a narrow and arguable point. Following are some useful tips that will help you in the process.