There’s a lot of tools out there for discovering keywords, keywords related to the keywords, building up a keyword network strategy, and so on. Here, you can do all of that for free using some Google search operator hacking.
We start with the tilde operator (~). (Ask a nearby Linux geek to find it on your keyboard if you’re stuck.) The tilde means “synonym” to Google; it will highlight the synonym words in bold when you use this. Next, we use the dash operator (-).
The dash means “opposite” to Google; in other words, leave out all pages which contain this exact word.