You play the Ace- that’s the easy bit.
If the suit breaks 3-3 it doesn’t matter what you do because you’ll only lose 2 tricks.
If the suit breaks 5-1 you are destined to fail whatever you do.
We need to concentrate on what happens when the suit breaks 4-2.
If the suit is divided KQxx opposite xx you will lose 3 tricks whatever you do.
However when either opponent holds Kx or Qx you can restrict losers to 2 by playing a small trump on the second round of the suit. You then play the Jack to force out the other high honour, followed by your 10 to draw the final trump.
PLAYING THE JACK OR 10 ON THE SECOND ROUND OF THE SUIT IS THE WRONG PLAY.