Well, the best places where there are social aggro mobs, almost flat ground (hills make it a bit harder, but still doable), mobs that don't cast (can do it with casters, but not for learning) and of course charmable mobs.
Places to look at PoN is a good place to do it at. PoD was a good place. Not sure if it still is due to the fact I think the spiders roam most of the zone now and they can snare you (BAD spidey!). Opps, stop listing places. Just realized you said you are 53. PoN and PoD require you to need the lvl 64 charm to do it there.
Pre-64 charm I would suggest Natimbi. Warning they did make a few changes since I was here swarming and some mobs summon. Do some tests first. Other than than I can't really remember any good places. I did some swarming in WL on the giants, but the trees get in the way and charm always broke fast. Guess you could always practice in EW until you get the hang of it. don't think you would get much exp there though.