Make it sweet. Not ruffles and lace sweet, because that still has a little cowgirl in it. This sweet is more Elle Woods. Pair your plaid with a cute skirt (a chic cut is best) then pile on the hot pink accessories. If nothing else, put a pink scarf in your hair and wear some pink lip gloss. This would work with any neon as well.
Make it tough. Pull a Johnny Cash and straddle the line between country and rock. Throw a motorcycle jacket over your plaid shirt. Break out the skinny jeans (black over blue). Pull on your butt-kicking boots with some tough jewelry. Now practice your icy stare. (For the record, Roommate is physically incapable of an icy stare.)
Mix it up. If you have a plaid that's low on color, try wearing it with another pattern. Don't wear them side by side though. Here I've separated the patterns with a blazer, but you could also wear your second pattern on your shoes, in your hair, or on a scarf.
I mixed things up a different way with this same outfit. Piles of gleaming metallic can't help but make your look slick.