Pre-heat oven to 325. Put ham in shallow roasting pan, positioned in lower third of oven. Bake fully cooked ham about 10 to 12 minutes per pound, until meat thermometer inserted into thickest part reads 140. Bake partially cooked ham 15 to 20 minutes per pound, until meat thermometer inserted into thickest part reads 160.
To glaze ham, remove it 45 minutes before it should be done. Cross-hatch top of ham with a sharp knife. Mix brown sugar, dry mustard and fresh orange juice and spread over the ham. Finish baking.
When ham reaches correct internal temperature, put it on a platter, cover loosely with foil and let stand for 10 minutes before carving.