As South, you need all six spade tricks and have plenty of entries to your hand.

How do you play the spade suit?

Lead low from your hand and finesse West for the queen on the very first round by playing the 10 or jack. If this wins, come back to your hand and finesse again.

Error:
Some players will cash the ace or king first and then come back to their hand and finesse on the second round. They They are guarding against the singleton queen offside.

This would be the right play if you held three small in your hand, but it's inferior here. To see why, picture East with a singleton. Now what are the odds that the singleton is the queen? Only one out of five! But a small singleton will occur four out of five times