An obvious one is just to use them a lot! The more you use a word when you are speaking, the easier it is to remember it. Another method is something like 'flash cards' in the old days, these were physical cards, with the word on one side, and either a picture, or the meaning in another language on the other side. Nowadays, you can get programs or apps that do that for you. They are a bit cleverer, as they remember what you got correct. I use one called mnemosyne, and there is another one called anki.

I agree with Gary and would also add quizlet as a way to learn words, you still need to activate them by using them. Keep a list of new words by your computer and when you want to add a new post on italki - try to include your new words. Hope this helps Bob

Anki Droid is best for me.

I would prefer Memrise. It's program for phones. You may load it in AppStore or GooglePlay