No worries, also check out evernote web clipper, it seems to be smart enough to remember to always put my clippings from these groups in the right folder.http://conference2012.leadingre.com/
Well, there's a softball in this group.
For signed, I think a handwritten note is a great follow up. Then, provide relevant status updates weekly, including new competitive listings, new contracts written in their area/price range, price reductions and solds. Be sure to provide them with the average days on market and list price to sales price percentages. These will come in handy for setting expectations. Additionally, list all marketing activities and showings and the results of those activities.
For soon to be signed, continue to establish trust. They already know you and like you, but they may not yet trust you sufficiently to hire you. After sending a handwritten note, follow up with similar market reports as you'd provide to your seller clients, lists of ways to prepare their home for a successful sale, invitations to your open houses, etc. They may need reassurance that they are making the right choice by hiring you over another agent.
I learned a long time ago, hire slowly and fire quickly. If people are trained properly, and expectations are clearly defined, then there will never be a problem. Admittedly, its easier said than done. As for your question, if you don't let them go now, the problem will grow exponentially. Fire them!