With DS1 I kept the baby calendar to keep track of things he'd done! I had professional pics taken of him at 2 months, 4 months, 6 months, 9 months 1 year, 18 months, 2 years, 3... every year after.
DS2 the baby calendar was not updated as much, but still pretty good! Had the professional pics done at 2 weeks (with older son's 2 year pics), then 2 months, 6 months, 1 year, 18 months, 2...
DS3 had pics taken at 1 week (with DS1s 4 year and DS2s 2 year pics)! He's almost 5 months now and hasn't had any other pics taken!

I'm hoping to get a 6 month pic taken!
I keep scrapbooks, but havn't been in a while - I'm WAY behind! I have a scrapbook for each of them and then a family album that I'll keep! I'm thinking I'll give them their albums when they get married, so I'll have mine to keep!
I try to get stuff journaled with each years pics, etc! But when I get behind I can't remember what they were doing at certain ages!! I was pretty good with ds1s, but getting worse with each kiddo!!
Sore subject for me too!