These are a few tips that worked for me.
1. Make flashcard. I usually write the new word on one side and different ways to use the word on the other side. You can also write the meaning of the word. It's easy to use, you can bring it with you anywhere and review it anytime. When we learn a word for the first time, our brains have a hard time retaining the information; however, if we see the word often and use it, the chances of it getting stored into our long-term memory is more likely.
2. Study words using categories. For example, if you're learning 20 word, maybe you can learn words in the same category and try to put all of the words together in a paragraph.
3. Watch a film. While watching the film note the words that you did not understand, along with the sentence. If you enjoy the movie, it will be much easier to remember the word and sentence.
It is difficult to remember all the words, but if you practice using it the chances of you remembering will increase. I hope this was helpful.