This post by my frolleauge (friend and colleague), William Masson is SO good that I urge you to read it in full.
In addition, here's my humble take.
1. You want to OWN your relationships. This gives you PERMISSION to stay in touch and staying in touch leads to greater donations, sales, activity.
2. Unless you have a cellphone number or an e-mail you don't OWN your relationship. Why? Because you can't reach the prospects, you can't court them, you can't take them to lunch. :)
3. Get serious about developing your contact list. All marketing starts with a good list. Ask everyone to subscribe, all the time.
4. Be a good steward/friend. DON'T EVER take your relationships for granted. "Do unto others and you would have them do unto you!"