Lauren,
To follow up on leads, I use a system called Intersend.com. You can assign leads to different campaigns based on what type of lead it is, ie. relocation, local buyer, etc.
Each campaign is pre-written with messages designed to make them respond to you. They get anywhere from 10 to 20 emails from you over the course of a few weeks or months based on the chosen campaign.
I've found most of the campaigns to be pretty effective, but I've had to tweak some of them to get better response. My best leads are relocations because they need and want information about my area and I can develop the relationship by giving them what they want.
I hope that's helpful.