I purchased a fat quarter from a LQS that was folded the neatest way. I hope I can explain it to you with these pictures. When fat quarters are folded like this, it makes them organized and easy to look at when choosing colors for a quilt.
fold the fat quarter twice, lenghtwise
then fold in half again
bring end with selveged edge up
tuck the folded edge into the selveged edge
this is what the finished fat quarter should look like