Fat means that the ribs have a good flavour so look for marbling throughout the meat and the ribs should be a pink-red colour. The key to good ribs is to marinate them well and cook them slowly ...
You need to take the pork out of the fridge about an hour before you cook it so factor that into your timetable, adding it to the 3 hours, give or take, that the pork will be in the oven.