After North opened a strong (16-18) No Trump, West made a good bid of 2 Spades which will probably make via 5 Spades, 1 Heart, 1 Diamond and a slow Club with the Queen. North thought he would get a "free" bid in of 3 Diamonds on what is a very poor suit and would be better advised to Pass. 2 Spades may not be making and partner is still there...
Tip 1 - DONT' BID YOUR HAND TWICE.
East took the "push" and bid 3 Spades which is now bound to go at least one off but South thought "Oh, partner likes Diamonds, I'll help him..." and bid 4 Diamonds. This came back to East who made a "Pairs" double. If you think your making +140 in Spades, then you must try and get +100 at least from the double.
This doubled 4 Diamond contract drifted one off, North eventually losing a trick in each suit.
South was at fault. North made one "bad bid" of 3 Diamonds but got away with it. When East bid 3 Spades, South shoud have kept quiet and gained +100 for 3 Spades -1. If North had passed 2 Spades. South could have used 2NT (NOT to play!) but as "2 places to play". North could then bid 3 Diamonds and pass South's 3 Hearts if she held Clubs and Hearts.
Tip 2 - USE 2NT AS "2 PLACES TO PLAY" in a competitive auction
Tip 3 - DON'T HANG YOUR PARTNER for "pushing" a little.