I've put off writing this tutorial for a while because the technique I'm going to describe falls into a category that I call a "cheap trick" but it's so useful and results in such razor sharp images that I felt it was time to commit it to words. Even though I stumbled onto it on my own I'm sure that I didn't invent this technique -it's probably as old as macro itself.
I do all of my macro hand held (the critters I go after are normally too active for a tripod to be practical) and I'm always looking for a way to brace the camera. I don't crop and composition is important (keeping the camera steady helps me to place the critter where I want it in the frame). Also the flash can't freeze all of the motion in the scene. No matter how short the flash duration is it will never be short enough to give you sharp details if there is a lot of movement. I'm convinced that a lot of the image softness that people blame on diffraction is really nothing more than a form of "macro motion blur".
One trick that I've been using to keep everything steady I'm going to call the "Left Hand Brace" technique, and here's how it works: I'll slowly take hold of the flower that the subject is on by pinching the stem between my left index finger and thumb. I'll then brace the lens on that same hand and focus the scene by sliding the lens. Since the flower and the lens are all on the same support (my left hand) when one of them moves they both move, so it's easy to keep everything perfectly "still" and I have a lot of control ever where I put the area of sharp focus. Another benefit of holding onto the flower's stem is that I can slowly rotate the flower and change the angle to get different compositions.
It doesn't always work, and it helps if the critter is hungrier than it is scared of me, but when I am successful at holding onto the flower I can get some very unique images that are razor sharp even when shooting at high magnification and Fstops. It also works very well when there is a lot of wind, since the critter can't tell the difference between the vibration induced by the wind and the vibration that I cause when I grab onto its perch. The image included with this tutorial is a recent example of what I can do with the Left Hand Brace method. You can see a larger version here