A good realtor is the number one thing you need! Depending on the landlord's experiences they may simply go on instinct, I have a good friend who simply interviews potential tenants and then chooses one. She has only had one bad experience in many, many years of landlording, however she is an investigator by trade so... I also work with landlords, especially those who have had a bad experience, that want the 'whole nine yards' credit check, criminal background check, eviction history, employment verification, references both personal and from former landlords, security deposit, possibly an additional pet fee and the first month's rent in advance, (not to mention, in our area, they expect the tenant to pay the realtor's fee)!
Any of these may pose a problem for the tenant, with so many people losing their homes to foreclosure, credit score is not nearly as good an indicator of ability and willingness to pay in full and on time as it used to be. And, while there are many more potential tenants, they are looking more and more for bread and butter rental space. They are not nearly as willing as they were a few years ago to pay for 'extras'.
For this reason, many more landlords and tenants are choosing to work with realtors rather than to 'go it alone'. If any of the things I listed pose a potential problem for you, you would be well advised to work wth a realtor who has experience with the rental market. We know creative ways of getting around any issues that arise and helping both landlord and tenant to feel comfortable with one another.