With fatty meats, freezing is the best way to store it. It takes some planning, but if you put frozen meat in the fridge the night before or in the morning (depending on thickness - you'll have to experiment) it will be thawed enough to cook.

As for where to find the best meat - I can't help you. I choose meat at the grocery with the most apparent fat - which isn't much. I get the "lean" hamburger (80/20) - it used to be called regular.