This is the one that I use when I record stuff. i have picked it up in one of my Avy classes, but I found that it is helpful. There are a few others out there, like the Brooks Range one.
This is a kit that I have been looking at, since it seems to have a ton of good stuff. It comes with pretty much anything you could imagine, and the price is right.
I used to have a field book from them, I am sure I still have it floating around somewhere. It is a write in the rain paper, which is always nice.
I find that both help me keep more consistent notes than writing on a standard pad and/or the back of my hand/duct tape on the pants.
Honestly, every year I say I am going to be more diligent about keeping track of the snow conditions I find, but I have been slacking off over the last 2 years. I still go out and dig my pits and look at the crystals, but I don’t always document as I should.