Emma's article has great ideas. I also find inspiration in Paul Nations's book, "Learning Vocabulary in Another Language". This book reminds us about the many aspects of a word (or word family) we should know before we can say we actually "know" it. As a practical matter, I recommend keeping a word file, one page for each word family, in which is recorded definition, pronunciation, and an example of usage in a sentence. The word file needs to be periodically reviewed to reinforce learning.