Defense Is So Simple.

Counting declarer's hand and declarer's tricks (winners and losers) makes defense much simple. One simple example which illusrates the latter point (counting declarer's tricks) is below:

You hold:
Q x x
x x x x
J x
A x x x

Your RHO is dealer and he opens strong 2C.
Bidding:
2C-P-2D(1)-P
2H-P-4S-P
4NT-P-5C(2)-P
6S-P-P-P

Partner leads Club Queen. Dummy is :

A x
A Q 10 x x
A K Q 10 x
K

Now plan the defense. Think before looking the solution.
Decalrer must be having K J 10 x x x in Spades for his 4S bid.
Now count declarer's tricks.
6S tricks (with Spade finnese), 5D tricks and 1H trick. i.e. total of 12 tricks.

If declarer has 7 carder Spade, then he might play for drop of Spade Queen, then you will get 2nd trick.
But there is one foolproof way of setting the contract. Partner is marked with Club Jack. So play a Club and force declarer to ruff the club in dummy. Now declarer cant take spade finnese to catch your Spade Queen.
A very simple defense indeed if you figure out the way in which declarer will be going about to make 12 tricks.

Prajwal