In addition to the good advice above: start a log book, and keep detailed notes of every mix. All the ingredients, quantities, as much as possible. You might want to keep a record of any special mixing or steeping methods, too, although I'm not as convinced as some that these make much of a difference.
Once you get something right, you don't want to have to rely on memory to do it again - especially as it often takes a fair bit of time and experimentation before that happens. I have to check my notes, even when I'm making a batch of something I've done numerous times before, in case I did something subtly different with that last batch that really worked.