If the cutter takes two steps, that means he is going all the way to the basket. He can jockey with his defender and move his shoulders back and forth and try to duck behind the defender, but the passer should not have to guess whether or not the cutter is going. As soon as the second step begins, the cutter is going. If both the cutter and passer are sure of that, the cutter can be led and can score even when he is very well guarded.
From Dick’s book Stuff
Welcome To Keys To The Gym 
Great players and great teams are often thought to have great decision making skills and as such are considered smart. But, I think it less about the decisions they make in the moment than it is about the habits they have that dictate their decisions. This two step habit is one of those things that would look smart but its not really be anything special to a team with good habits. It is simply how they play.
Great backdoor cuts can come off of 2 reads:
1. The obvious read is if your defender is aggressively overplaying you and is in your passing lane(especially on-the-line, up-the-line).
2. The second less-obvious read which most offensive players miss is when the defender turns his head to locate the ball. In that split-second, the defender is not watching his player and is susceptible to a back-door cut, even if he is laying off in help position.
Point number two is good one Rakesh. Anytime your defender loses you, you have the potential to be dangerous. The key is that you have to take advantage of that gap and actually get dangerous, cut somewhere that makes you a treat to the defense. If you do this and do not get the ball, that is likely because you have gotten help defenses attention which potentially creates opportunities for others. We’ll talk more about being “dangerous” as we go. Its one of those this common sense things that is remarkable uncommon.