Skin before hang, always, always, always. Also, cut away all the fat that can reasonably be cleaned off, clean off all the hair/etc, and then wipe down all exposed meat with a water/vinegar solution (almost all water with a decent splash of vinegar).
The latter bit changes the PH of the 'film' that forms on the meat so you wind up with nice pink/red meat all the way to the surface, without loosing any to the black crusty bits that form otherwise.
Also, aging is the natural breakdown of the meat, which is controlled by temperature over time. The higher the temp, the shorter the time. For examples, if you are aging at 32 to 34 F at a very constant temp, I will age as long as 30 or 40 days, and have some of the best meat you ever ever ate. Aging at say 42-45 F fairly constant, give it maybe 7 ish days (and you'll get almost the same results). You can get also pretty decent results aging as high as low 50s, but only let that go maybe 2-3 days - and that will still produce pretty good eating. Any higher than low 50s during aging, and you will need to stop aging and start cutting before the rigor mortis has let go, and that... will be some very tough meat.
All that said - for the very best results, I don't even hang meat anymore, I wet age -- debone it, vacuum seal, and huck it all in a refrigerator for about a month at 34 ish degrees constant temp. I loose near 0 meat that way, and I've lost count of how many friends who used to be like "ewww, nasty gamey deer meat, how do you eat that?", who now think deer is better than beef after my wife and I fed them some of our venison.
