Deliberately throw your lens out of focus.Experiment with throwing your lens way out of focus on purpose (you'll need to take your lens off autofocus to do this). Out-of-focus flower images can be hugely colorful and wildly evocative.
Generally, this works best with a telephoto lens and a wide-open aperture. If your photo is out of focus, you want people to know that you did it on purpose and not think that it might be simply a mistake.
Shoot on a mirror.One of my most used props for flower photography is a mirror. This is inexpensive and easy to find. Go to any window-repair store and order a piece of mirror-backed plate glass. A small shooting surface (18x24 inches) should cost less than $20.
Try backlighting.Many flowers and their petals are translucent. This means they're excellent candidates for backlighting, where the primary light source comes from behind the flower rather than being reflected from the flower's "face." You can backlight a flower in the studio, and this also occurs naturally when you're shooting through the flower toward the sun. Some of my best flower "portraits" are shot using backlight.
Keep a piece of black velvet handy. My favorite way to isolate flowers is to drape a black cloth behind them. You can do this in the studio, in a garden or with wildflowers. Black velvet works best because it's very light-absorbent and doesn't have an obvious pattern or nap. You can buy black velvet inexpensively by the yard at any fabric store.