The 'best' probably would be the spray in 'foam' insulation. It seals all air leaks and provides a better fill. The downside is that is is more expensive. If you can not afford it, be sure to use some spray foam (comes in cans) to seal all cracks & openings thru exterior walls. Then, use a good house wrap to further seal air leaks. Be sure to seal all window openings (around edges) with a slow rise foam spray so as not to 'bend' the framing. There are literally hundreds of potential air leaks thru the walls so try to get as many as possible. That said, any good insulation will suffice if the air leaks are stopped.