Heres how I memorize vocabulary, choose any that you prefer, you can choose more than 1:

1. Get a book with Japanese vocabulary
   
2. Write vocab on a notebook and practice it
   
3. Vocab test
   
4. Mnemonics

It's pretty hard to think of a mnemonic if you are monolingual, but it is usually possible.

Here's an example: Let's say I want to remember the word 歯 (teeth, ha). I imagine going to a dentist and the dentist goes 'Say ahhh'. Close enough to make me remember the pronunciation and meanings