I have the following tip for RTM users:

It's hard to remember to keep in touch with friends that have moved away, co-workers from previous job, professors from college, and so on. Nevertheless, networking is really important for both personal (not losing touch with old friends) and professional (your new gig might come from a person you worked with in the past).

My tip is to use a tag like #keepintouch and repeating events (repeat every X month) to make sure that you are staying in contact with others. I make a task for each contact (but I hide this tag from my main lists and use a smartlist to just show me the people I should ping this week). This can remind you to shoot that person an email, make a phone call, or even send a real letter.