In rock/pop music, "12/8" is often 12/8 compound time - i.e. 4 dotted crotchet (1/4 note) beats to the bar. This is the equivalent to 4/4 (common time) with each 1/4 note divided into 8th note triplets. The main reason anyone would prefer to call it 12/8 compound time is if it was being written down - it just saves on having to write down all the little triplet bars etc.
Either way one can easily count the bar by accenting the 1/4 notes: 1-2-3, 2-2-3, 3-2-3, 4-2-3
A good recent example of this would be The Captain by Biffy Clyro - with Ben Johnston being their rather superb drummer.