How should I augment my vocabulary?

Other than reading/a dictionary, how might I augment my vocabulary in such a way that I can readily use new words in writing and in conversation?

I’m taking the little knowledge quizzes at that freerice website, and the vocabulary quiz is the most fun for me. Sometimes though I have to guess, and even the words I know are rarely available to me while speaking or writing.

(Also, if you have the time and interest, there’s a tough vocabulary test here and it would be cool if you could share your results with me here or in a PM. I got ~150 but that was a while ago.)