Because people call me to collect swarms I don't really have to place traps, but since you asked, here's some input that may help.
Certain trees will attract swarm clusters. Find out which ones do for your area. Sounds a little crazy but its true.
In my area: lemon/citrus trees, Holly bushes & Holly trees, magnolia trees & lastly, chinese tallow trees (mostly in May, early June)
Any known bee tree for obvious reasons. Any known bldg (particularly apartment complexes) that have had colonies prior.
Apartment complexes are usually somewhat lax when it comes to maintenance issues and they are just downright swarm magnets. And on top of that, I've come to find they usually take the cheapest route when it comes to bee removal, at least for some time.