I just bought a Nikon D5000. It is my first digital SLR camera and I am having trouble with the autofocus. For some reason almost all of my pictures--at completely different apertures and speeds--do not look focuses when I put them into IPHOTO. I have read about autofocus in the manual and also in David Busch's guide to the D5000, but I found them confusing and I am still having trouble. Can you give me some simple instructions that might help me?