Hi og6,
The best weight to hang for hanging is a low weight usually (2-5 lbs) and then you want to hang with that for a few weeks to a month slowly conditioning your dick (making it stronger for the heavier weights) as you slowly up the lower weights. Then after the initial conditioning phase you should start to see gains as you slowly up your weight to higher weights (usually people start seeing gains around 7-12 lbs). BIB said the weight that you start gaining at but is the lowest possible weight to gain at and you still get fatigue the MAX WEIGHT. So as you slowly condition and grow and go up in weight your max weight will go up slowly.
One thing to remember is too not make the mistake I and so many others here have and rush too much and use too much weight. There is such a thing as overtraining in PE and this will only slow gains. Also if you up your weight too quickly you might condition to quickly and slow your overall gains down.
The feelings are always some of the hardest parts to describe because of course everyone percieves/interpets there own body differently (different pain thresholds). I would generally say that you should get a certain type of fatigue/soreness type feeling in certain parts of your shaft depending on the type of hanger you are using and the angle of hanging you do (SO, SD, OTS, BTC, OTL, SU, fulcrum, etc).
Be paitent, that is the key! This is a marathon not a sprint as they say. If hanging does not work for you then maybe give ADS/extenders/traction stretchign a shot but that too takes a lot of paitence. Good luck, I hope you get good gains.