This is one of the techniques that I used to use as I was doing some self study on a language during my university years. I was trying to learn French but I was aiming to learn only the spoken language for practical reasons at the time. A good friend of mine was quite fluent and accurate in that particular language, French, and he was kind enough to help with especially vocabulary. I used to learn words and their meanings (as well as some grammar points) from him and then using my own strategies, I used to memorise them.
Below is one of the methods I used and found helpful then. It can be used for whichever language you are trying to learn and it is practical and easy. You can also use this technique for phrases, idioms, opposites or synonyms too.
Just cut up some blank double sided paper into squares. The size is upto you but I believe that 8x8cm should be appropriate enough. On one side, write a word (or an idiom or a phrase) in the language that you are trying to acquire and on the back of it, depending on your level, write the definition/explanation/synonym/ in either your native language, especially if you are a beginner, or in the same language as the one you are trying to learn. Then, fold it in half and then fold it in half again. So, it becomes a little square and you cannot see the writing on it.
What I did with this was that I put may be 15-20 of those squares in one of my pockets at a time (this was particularly easy especially during winter when I had big jackets with pockets on me). Every time I had a chance, I took one out of my pocket, read the writing on one side, and tried to remember the info on the other side without looking at it. If I remembered it well, I put it in my other pocket. If I wasn't sure or correct, then, I put it back into the same pocket. At the time, I used buses for transport quite a bit and the travel time on buses gave me a lot of practice time. You can do it wherever and whenever suits you. This activity is pretty flexible and is easy to personalise.
Have a day when you learn something new and useful today!