Source: Trick One Guess in a Matchpoint 3NT
Try planning the play for this hand at matchpoints.
Opening lead: 
6
Declarer has a guess at trick one but should play the Jack from dummy rather than the nine. With only one top honour missing it is more likely West will have led from the Q than the 10. West may have both in which case it does not matter. If the opening leader only had the 10 she may have chosen to lead a higher heart in an effort to stop partner returning hearts.
The J wins in dummy and now Declarer is safe for at least nine but wants to make as many as possible. What should you do now?
As you are in dummy you should run the 
10 from dummy, but not just because you are in dummy. It looks like West has led from a five card heart suit and therefore East only has two hearts and therefore three more unknown spaces in her hand and more likely to hold the J than West.
Here is the full deal: