One way to improve your vocabulary is to read often. And by reading, I mean slow down and take out the words you do not understand. Look them up with a dictionary and write the meaning down, also read the example sentences that may be in the dictionary.

For grammar, I suggest you get a good book with exercises and simple lessons to practice. I recommend The Good Grammar Book by Oxford. It has good explanations and activities to help you. It is also used by a lot of language centers and is reliable.

Hope this helps

http://www.oup.com/elt/global/products/goodgrammarbook/