Possible ways to organise your vocabulary include relating new words to your own personal experience (e.g. if you learn new colour words, what things do you have in those colours - a purple sweater, an orange mug?). You can also divide your notebook (whether paper or digital) into topic areas (e.g. words to do with food, with travel, etc.). You could keep a digital notebook on your computer or mobile device; lists or words you type in can then be sorted alphabetically or searched very quickly.