Read Voraciously
Reading voraciously simply means to read often and a lot. This strategy is number one because reading is the very best way to get new vocabulary. Everyone agrees with this. That's because when you read, you also see how words are put together to make sentences. This makes reading more natural and realistic than just memorizing word lists.
Reading gives you a chance to use context information. Let's see what context means. You see how each new word is used in a sentence. So, the words around the new word help you guess its meaning. Guessing meaning from context is the natural way of learning a language. This makes reading your best chance to try this natural way of learning.