If they are hanging on a tree limb, they're just tired. Give them their space and they will usually leave within a day or two after they've had their rest.
If they don't leave after a few days, or if they have taken up residence inside a structure, you will probably want to contact a beekeeper for bee removal services. Bee removal services to homeowners and commercial sites are part of a beekeeper's business, so you should expect to pay a fee to have a swarm removed.
Do give the bees every chance, since bees are an important resource and shouldn't be needlessly exterminated. Here's a link to more information on local bee removal services:
http://uccemg.com/General-Gardening/?uid=4&ds=548