I take pictures of my scarfs. It's fun to look at them as i can see where i am making headway being a new knitter.
I also save the label of each yarn and write on it what i used that particular yarn for just in case i want to buy more.
Good example. I went to the LYS yesterday looking for a certain yarn i had used and loved. I could not find it. Saleslady ask me what the name of the yarn was? If i had taken the tag with me i would of known.
After much searching we found it in the discontinued bin.