Providing it is safe to access the swarm he may put on his beekeeping clothes - overalls with a black gauze hood and leather gloves. This is simply because he will have to disturb the swarm inorder to move them. He might spray the swarm with a weak sugar solution just to 'calm them down'. He'll then place a box or skep below the swarm - this will be used to transport the swarm to a temporary home. He will then shake or bang the branch on which the swarm is settled.
Swarms are surprisingly heavy.
The swarm pictured above was a large swarm weighing 26 pounds - most are much smaller. Most of the bees will drop into the box, the rest will take to the air. If the queen is in the box the bees in the box will point their bums in the air and beat their wings like crazy. The flying bees will join the swarm near or in the box. Now the beekeeper waits for a few minutes to let most of the bees join the swarm in the box.