The best set up to attract a swarm 

I put empty hive boxes out a month before spring swarming impulse starts and often get swarms in them , the scout bees are often seen inspecting the boxes , if they are happy they will move in when they swarm , I have even had them move into 5 frame nucs. I do put a comb or 2 in them ,it helps them to get started if they move in .