I have been using the shipping tape to the stock or scope for a long time, as usual, simple works best and is economical to boot usually.
If you or your family happens to have laminating tools, that will get you a few degrees nice, especially if you use the tagging method Tom mentioned. Another that is cool, but a little expensive is the Leupold retractable ballistic chart, mounts on your scope like a scope ring, has a retractable steel tape like a tape measure that is 6" to 8" long and you put your data there, about 35 bucks at Midway, item #168466 for 1" scopes.