You make it fall into a box. Shake the branch they are resting on, or brush them off until they fall. You cant tell if the queen made it into the box depending on the behavior of the workers already in there. If you missed it, goto step 1.
We had a swarm in our orchard at the weekend and I watched a local beekeeper do exactly this. The queen must have gone into the box as all the bees still left on the tree or flying around soon followed into the box.