Bring out the books - Reading is a great way to build your English vocabulary. Reading can open the treasure to an endless vocabulary and has hundreds of other benefits.
Look up new words - Instead of just taking in the meaning of the word, do some research on it. Read it in context to other words and sentences.
Keep your ears and mind open - You can listen to other people, and how they use different words and pronounce them to not only improve your English vocabulary.
Keep a pen and paper handy - Make a note of any new word you read and hear. Write down its meaning and context and try to use the word as much as possible in your conversations.
Read dictionary and thesaurus - Reading a dictionary or thesaurus can greatly improve your English vocabulary. And, you might actually enjoy the whole process of it.
Just write - Make sure that you write for at least half an hour every day. Keeping a journal can be a great habit and can help you improve your writing skills and vocabulary.
Use flashcards - A quick way to build a large vocabulary is to study a number of words via flashcards. Aiming for one new word a day is reasonable.
Challenge yourself - Challenge yourself and test your verbal and oral communication skills and how far your vocabulary has come by taking online tests.