I started a journal on my first garden year. At first, I noted everything. What type of plants I got, where and when I planted them, and noted every change for the whole season. It was for learning purposes really. I also took pictures of everything about once a week or so to match up with my written notes. This year, I did the same thing, but I didn't record as many details unless it was a new plant. It's just a hard cover notebook that I bought on clearance a while back. lol nothing special. I also kept the plant identification (thingy) for each species of plant I have.
I learn best by hands on work, notes and pictures. lol