I just bought some montec G5 broadheads to try them out. They don't seem to be very sharp. What is the best way to sharpen them?

They're good broadheads and have the reputation of being hard to sharpen and not very sharp out of the package. I use them and I sight in with them before sharpening them, no sense in sharpening them and then sighting in and having to resharpen them. When sharpening them I screw them onto a short 8" piece of arrow shaft and just push them across the stone keeping them flat, rotate to the next side and repeat making the same # of passes on each side. I use a fine diamond stone to get them close to sharp enough then use lay a piece of real fine emory cloth down and make about 20 strokes on that and finsh with a crock stick. They have directions on their web site.