Only three! Try this on for size...
Step one is to research the company first, you may not even want the job. Most people don't do this and rue the day they accept positions because they didn't do research.
Now armed with the facts, go forth and make your questions.
However, the real sleuth goes to company watering holes and other events so that they can slip in and find out the real story in unguarded moments. I keep names, numbers and emails, which I refresh regularly because you can often get direct information from someone who knows someone.