Make sure you have a solid premise

The premise is a statement that makes a tentative assumption.

Throughout an investigation -- regardless whether its a two-day or two-month investigation -- you will test the premise against the information you gather. In the professional world you will have a difficult time getting your editor to greenlight a big story if you can't frame it in a focused premise. They'll fear you are on a wild goose chase. Here's how you do it: Start with a question that can't be answered without significant reporting. Then turn that question into a statement.

Question: Are they building that new athletic building on campus right?
Premise: There is something wrong with the way the school is constructing the new athletic building.

Question: Why is it so hard to park on campus?
Premise: The school seems to be issuing far more permits to park than there are spaces.