When out in the garden itself, I use a small (3" x 5" or so) spiral bound notebook. I can scribble down notes easily, and stuff it and the pen into my shorts/pants pocket if need be (more usually I stick it back into my caddy, which also has a plastic ruler and a tape measure and other things). In fact, if I am only measuring bloom sizes, I just use the ruler - I can juggle that and the notebook/pen easily. (For measuring scapes, I just wait until dead-scaping and then cut the scapes and bring them back to the patio table to measure; with the caddy/tape measure/notebook all on the table, no hassle.)
Back inside, I tear off the day's pages and enter that data into the computer, leaving a fresh page for the next day's notes.
Unrelated to record keeping, sort of, I find the notebooks extremely useful when pollinating. I don't like having to clip/mark the crosses as I go; instead I madly dash around with the pollen in hand, hitting everything that I think will be a good mate. I do this for a few pod parents (same pollen parent), holding those parents in mind (like a mantra
), and then go back to the patio table and jot them down in the notebook. Rinse and repeat. After all of the pollinations are done, then I can go back and clip the crosses at my leisure. (I almost never use different pollen parents on the same pod parent on the same day. If I do, then I make certain to keep track of which pollen parent was used on which blooms, either by clipping the first set of pollinations before proceeding with the next, or else writing down which blooms were pollinated by which parent ("back 3 blooms x X, front 2 blooms x Y").
All of this now reminds me that I should probably go and buy a new set of notebooks for the year (also useful for making notes when hiking, I might add).