When you have a house all set and ready for renters, the last thing you want is to be qualifying deadbeat tenants.  I have learned over time that the harder you make your phone interview process the better chance you have of saving yourself a drive.  Also, when you do show the home, your chances increase on getting good tenants.

For instance.  Instead of letting the potential tenant control the conversation, turn the questions on them. When they ask you how big the house is, tell them and in turn ask them a question.  "How soon are you looking to move in", is always a good one to ask.  

Also, make sure the tenant is ready to move.  A lot of times, tenants start looking around 2-4 months before they are even ready to move in - they may even want to see the home - this is a waste of time.

Next, you need to know about their financial situation.  Let them know that the security deposit and first months rent are always due before move-in.  If the rents are high, like 1200-1400 a month, this can cost the tenant a lot to move in.  Make sure they are aware of this before you even show the home.  Many will back out for this reason alone.  At least you didn't waste time showing the home.

Lastly - never show your home if you don't feel comfortable with the person on the phone.  If the prospect can't answer your questions or you don't think they qualify based on the way they answer - you don't have to rent to them!