The Problem Pool Balls

You have 12 balls identical in size and appearance but 1 is an odd weight (could be either light or heavy).

You have a set of scales (balance) which will give 3 possible readings: Left = Right, Left > Right or Left < Right (ie Left and Right have equal weight, Left is Heavier, or Left is Lighter).

You have only 3 chances to weigh the balls in any combination using the scales.

Determine which ball is the odd one and if it's heavier or lighter than the rest. How do you do it?
 

Puzzle supplied by Richard Rider
 
 

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