The one major hindrance when it comes to shotting macro is the weather; more specifically, the sun and the wind.

Since flowers don't always point towards the sun, you may have to rely on a different light source in order to illuminate the inside of a flower. This additional light source is usually the built-in flash on your camera. Alternatively, a speed light that attaches to the camera hot shoe is preferable, not to mention more potent than any built-in flash bulb.