(This tip is for younger writers, like myself)If you do not know what a word means, but you think it sounds impressive, don't just think, "Oh, no one will mind. I'm sure that truculent means a truck that my brother borrowed."
If you do know what a word means, and it fits in with the scene, then USE it. But if you don't, LOOK IT UP IN A DICTIONARY! A thesaurus is also great.