The best way to improve your English on your own is reading a lot of texts in English and write out words from this. Later , ask your friend/parents/sliblings that you asked the words. As the same as my predecessor, he/she is got right too.

Greetings to all : )

Well, the best way to improve both grammar and vocabulary is reading and writing everyday. Practice makes perfect!

Besides, I suggest keeping a notebook, collecting things you like in English like prose, poems, quotes, etc. When you have time, revise them. Also take advantages of relaxing time, for example, watching movies or listening to songs. Pay attention to the script or the lyrics. 

To remember some specific words, you can make up some stupid story or even draw about it. The principle is the more stupid it is, the more easy it is to remember.

Hope that helps!