I screened my first tenants using a realtor. Before you scowl at the idea of paying somebody comission to fill your units hear me out. I spent 3 years doing research, reading books, trolling BP forums, attending seminars, investors meetings, blah blah - still nothing can prepare you for screening people better than, well, screening people. Also I had just about run out of money doing rehab and wasn't eager to spend a months rent on my agent.
By using my trusted agent (with prior relationship) I was able to appeal to a broader audience (showings at any time, MLS listing, craigslist, current clients, calls, emails) without spending my own time all while being kept in the loop and watching the process.
My agent was far better at qualifying people and pitching the rental than I and it was important from a legal standpoint to say the right things. He provided all the application forms, landlord disclosures, etc. For that money I learned how to screen, what to do/say, what forms to use, and now I have SUPER tenants who I appreciate every 1st of the month. There are many techniques for screening and I'm sure you'll learn them all but for your first time around....