A while ago, I started a new project: keeping a journal specific to my kids. I keep a journal about my life in general (something I started doing when I was 13) but I figure my kids won't want to wade through that to find the fun parts about them when they haul these books out of my attic after I'm gone. And there are parts I don't want my kids reading -- even if I won't be around to deal with the aftermath!
Every week or two, when my kids do something cute or memorable, I write it down in my "Life with Little Ones" journal. I had forgotten when I'd started it -- I'd thought a few months ago -- so imagine my great surprise (and happiness) when I realized I'd actually started in August 2010. 16 months is a lifetime when you have a 4-year-old, a 2-year-old and a baby. I got to read about Sam's first words, his first steps, and Jasper's various stunners. Like when we talked about moving to our new house, one night he called me into his room and said "I'm sad." I sat next to him and said, sympathetically, "yes, it's sad to leave your friends." And then he said, "No, I'm sad because I want you to bring me water." Ah.
Anyway, it's been a small investment of time to keep the diary, but hopefully a big payoff in memories. It also helps me remember how and when my kids have learned various skills -- Jasper in particular with writing letters and numbers and then his current interest in math. Children take up a lot of energy, and so often it's hard to remember specific things, but writing them down has the memories flooding back.
How do you preserve memories of parenthood?