pock•et (p k t)
n.
1. A small bag like attachment forming part of a garment and used to carry small articles, as a flat pouch sewn inside a pair of pants or a piece of material sewn on its sides and bottom to the outside of a shirt.

pock·et·ed, pock·et·ing, pock·ets
1. To place in or as if in a pocket.
2. To take possession of for oneself, especially dishonestly

Idioms:
in (one's) pocket
In one's power, influence, or possession: The defendant had the jury in his pocket.
in pocket
1. Having funds.
2. Having gained or retained funds of a specified amount

To K(no)w ones Pocket.. To never live inside the pocket of another
To Know ones Pocket.. To understand, participate and experience in ones scene
To Know (what is in) ones Pocket.. To understand financial value of your experiences, or mental inventory of ones actual pocket

Promotions, Productions, DJ and Review the rest is up to you..
Experience will tell you.. you must Know ones Pocket!!