For active or "near-active" clients, I use a large calendar to see a month's view of activity and all of the pertinent project dates associated with each client.  On the side of this calendar, I keep a list of clients who will require contact to keep them moving forward or (in some cases) to stay in touch to be able to gauge their timing.  It's a low-tech approach to managing detailed project dates, AND I never write the name on the list until I've done something FOR each of the clients I'm tracking.  It gives me a reason to stay in touch and to be useful to the client instead of just a general contact that may actually be considered an interruption to the client if I wasn't providing something helpful.   One of the "helpful" actions is to provide a list of recently listed or sold homes within the clients' neighborhood or area.  Knowing what is going on in the market helps the client and it helps me to not be caught off guard as to where the values are heading in their area.