I use a coil notebook with enough space to record both the recipe and a reasonable amount of notes. We're not talking a dissertation on quantum physics here, but a few lines. 6" x 9" maybe?
For indexing, each batch I load gets a unique alphanumeric identifier corresponding to the date it was loaded.
For example 040818A was the first batch I loaded today (04 day, 08 month, 18 year, A for first batch if there's more than one)
The same number gets Sharpied (fine point) on every rifle round that goes in the box.
The note book goes to the range with me during load development to record velocities, group sizes, air temps, etc.