I'll give a slightly different opinion.
1 - get a macro lens. They're MADE for macro, and the one you're using doesn't give a 1:1 reproduction ratio, so not "true" macro, although you could call it "close-up". That's not a biggie, the final image is all that matters, but just sayin'...
2 - shoot Manual Mode, manual focus. Period. Set your shutter speed at 1.5 times the focal length in use (or faster if you can), aperture to somewhere between f/11 and f/32 (you'll probably use f/16 to f/22 a lot). Auto-ISO on. Use a flash, built in works fine for most stuff, but a bigger flash and diffuser of some sort are better. Or make a homemade diffuser or bounce card for the built-in flash, pretty easy.
3 - yeah, yeah, like everyone says, tripods and beanbags are great. I never use them. Stuff rarely stays still long enough to set all that up, and most of the time you can't get close enough with a tripod. Shoot hand-held, and focus by moving your body closer and farther away, looking through the viewfinder. Takes practice.
4 - PRACTICE. Play with exposure. Maybe you need to up the flash output by +2EV, maybe you need 1/500 because the flower the bee is on is swaying slightly in the wind, etc, etc.
Here are 2 examples. Both are hand-held, and using the on-board flash. The 1st is with my Sigma 105mm Macro, which gives me 1:1, the bee was TINY, and the flower was moving around in the wind a good bit. The 2nd is MUCH trickier. It's a 3:1 (approx.) shot with a reverse-mount Nikkor 24mm lens. The greater the reproduction ratio, the smaller your DOF and working distance will be, so you have to move your body VERY carefully. Plus, with the lens reverse-mounted, you have to use a finger to hold the aperture arm fully open, right up to the last second before you take the shot, because when the lens is stopped down to f/11 or more, the viewfinder is pretty much completely dark. The grasshopper is less than an inch long. As you can see, I didn't QUITE nail the eyes in focus, but pretty close.