
The biggest being STOP over sharpening and learn how to FOCUS properly (or figure out why your camera wont focus!), then you wont need to over sharpen.
(seriously though, Im 90% convinced my firs dslr had back focusing issues... that or I really was just that oblivious too late to tell though, but its my biggest cringing point when it comes to my first DSLR. I never had the same issue with any other camera though, so who knows!)