they let go of aging and overpriced players. they scour other teams for developed, bargain priced players. they take risks on players with immense talent that have red flags (this sometimes works, sometimes doesn't...but they are always called genius for it). and a lot of times, free agents flock to NE for the chance to win a ring. but mostly, they have the best qb to ever play the game, arguably the best coach ever, and a reputation as a perennial sb contender.