The other answer isn't wrong but it really doesn't cover the read option exchange. It isn't that complicated and I just coached (the youngest team I have ever coached) a group of 2nd graders that ran the read option very very successfully. Here is what the play comes down to.
- Unlike most run plays, this hand-off includes very little movement from the RB. He may be moving forward but it is slowly. On most run plays the RB would be expected to explode through the hand-off.
- The QB should commit a push of the ball into the stomach of the RB. Not "Drop the ball". When the QB and RB are on the same page they will be comfortable in the read timing where the RB will hold. Sorry I have never put a stop watch to this but it is less than a second and a couple of 2nd grade RBs had it down in the QB really had it. So during that read phase of the play the RB will be in an athletic stance with arms spread to receive hand-off. He will instantly move forward with the ball on push. With no push he will rely on the practiced read timing or he will move instantly as QB disengages the ball. Note that there can be a push and a pull. If the QB really wants to sell it they can push which will cause the RB to start their sprint and grab... But it is the QB's job to make sure they secure the ball back ASAP (and a little bit of the RBs job to not wrestle for the ball or stop running).
So as a coach there is technique (QB looking at right spot, QB turned right, RB turned right, RB forward slant but not running), there is read time (some refer to as the mesh), and then there is the execution of the push or disengage.
I would like to add that a true read option is having an unblocked man at the line of scrimmage. The QB is attacking the movement of that person which allows the offense to play 10 vs 10 - usually at least one offensive player is negated (the QB) so the defense always is one player up.
Since the read went to the NFL, NFL coaches learned (albeit painfully slow) that the QB is a runner in that play and not a QB by rules. Meaning that if a QB runs a read option they are fair game to get whacked even if they don't have the ball - if they even give the smallest fake. So the NFL coaches (I could give you the exact game it changed) reviewed with the referees and made sure their "readed defensive player" could just lay out the QB. (the end of the Colin era)
Well this quickly trickled to college/high-school/peewee level. And I had a son that was a very small D1 DE/DT and if you ever ran the read against him you might as well get the trainers on the field for the QB. RB got 7 yards, well that's OK because QB is gone. Just standing there doing a fake and BOOM. I can't remember how many times in games he would just kill the QB, the ref would come over and say take it easy, he then asked the ref if it was illegal, ref said no, and boom QB nailed on the next read option - honestly I can't ever remember a team running the read option vs him more than twice.
And... why I mention this.
Most read option plays aren't really read options. They are a RB/QB fake mesh which looks exactly like a read option except that the QB is no longer reading an unblocked player... which means it is really just an option. But we call it a read option because it is a QB in pistol or shotgun with a mesh/read with a RB that looks just like a read option. There are a few teams that run the true read option but this is few and far between as they don't want to risk QB injury or fumble. Most "read option" plays are normal blocking and QB just doing what he wants based on defensive alignments and stunts.