I have trouble photographing light colored things like bright white flowers. I can't get the details to show up without putting my hand behind the flower and even then it doesn't pop out like I want. Is this due to shutter speed?
Or if your camera allows it, try setting it to under-expose by half a stop, or maybe a stop.
Play with different amounts of underexposure to see what the effects are
Just another thought on geting better shots, try using a tripod, or gorrilla pod, then put the camera on a timed shot, it just removes the hand jitter, which is inevitable with close ups.
As you have a Canon, take a look at CHDK (google it), shoot the pic in .dng format then use the free Lightbox app to play with corrections. It won't help the focus much but it does a good job of correcting exposure errors and allows you to play with different settings to build experience.