I rate my clients in terms of whether or not they send me referrals, would send me referrals if they knew how and those who I want to keep in touch with.  If I don't want referrals from certain hard to work clients (because people know people just like themselves...) then I delete them. I set up a communication plan and my crm tells me when to call, email or visit them based on the communication plan.

My CRM work handles those tasks.

I have my "A" clients that I call every quarter just to chat, take to lunch or coffee.   With business really busy, it is taking longer to accomplish this.