Antonyms

Fairly straightforward: KNOW THE WORDS.

Suppose you get hit with "AVER".

Now what? If you're one of the few people that knows the definition of AVER, great, find the word that means the opposite and move on. If you don't know what it means, well, there's not much more that you can do but decide which one of the first five letters of the alphabet is momentarily your favorite.

So, start memorizing some words.

Flashcards are the easiest way to learn words.