Do you really want to work with expired listings right now? Most of them are "soiled goods". 80% are unrealistic about price and that's why they didn't sell. Another 15% have issues and that's why they didn't sell. Only about 5% didn't sell because the first agent "didn't market the home properly".
That being said, if you DO want to prospect for expired listings, then I'd get ahold of Borino's Expired Plus course. It's covers all the bases and is the best approach overall.
Oh, and there are three ways to prospect to expired listings.
1) By Phone - Pros: Fast and easy to do consistently, low expense. Cons: phone #'s can be hard to find, people don't answer. Crazy competition.
2) At the Door - Pros: low cost, no need to worry about phone numbers. Cons: time, can drive there and have the people not be home. Not easy to be consistent and not easy to be first in line.
3) Mail - Pros: don't have to worry about whether people are home or not. Cons: everyone's doing it, low response rate overall, you have to mail to a large pool of expired listings over time to get results because people don't respond to mail as well as a phone call or an unexpected drop-in. This means a mail campaign becomes rather complex, labor intensive, and expensive.
By-the-way - Borino suggests doing all three of these activities at the same time as there is no "magic bullet".