Don't exchange your Justice Points!!
Save them for Cataclysm 85 raid-entry items!!
This is very obvious, but many people don't know what they're actually saving for.
At the moment, the Justice Points cap is 4000.
Here's a list of the items that are purchasable with Justice Points.
More specifically, these are the items that we are saving for (1250-2200 Justice Points).
In any case, the main idea is to save for these entry-level raid items that offer whopping amounts of hit for every class (3.5% out of 8% for hunters from 1 item).
Quite common sense, yet many fail to recognise.
All the best,
Syncness