Another macro technique I picked up is reverse-lens photography, where you mount the lens backwards on the camera. So instead of reducing the image to fit on the sensor, the lens magnifies the image. Combined with an extension tube, you can get serious magnification. And a boat load of light loss.
The down side to reverse-lens photography is the camera no longer controls aperture, so you have to do it manually with an adapter ring. When you stop down, the view through the viewfinder is stopped down, making it hard to see anything, let alone focus. Live view, once again, comes to the rescue. At least on a tripod. If you're hand-holding the camera trying to shoot out in the field, I don't know how useful it would be.