Reading is the best way, for sure. I found that reading and doing the exercises in this book helped me to understand the etymology and meaning for tons of words that I'd normally get tripped up on when reading new books. You may want to acquire it (library, possibly?), have a go at it, then use it as a jumping-off point for the rest of your reading adventures.
Deal link: Amazon
No single technique works for everybody. You can use wordlists from Quizlet or make it yourself from Wordnik. Some people also use Mnemonic Dictionary and the book Word Power.
If you are are looking for learning the words for long-time, I'd suggest using Wordnik and using them in your vernacular. Magoosh has used a lot of words with a high probability of occurrence in their questions. You can use that as well if you want. Here's a concession if you intend to use it.
The most important thing is to make the words a part of your speech and writings.