Are there particular written rules about when and where you can place structures? And then can you guys fill me in on some of the unwritten rules such as best materials and so on?

Depends on what entity manages the lake...some don't allow, others require prior notification and location, and others don't care. Be sure and check with the managing authority for the lake you are planning to place.

I like willows and Bo dark tree limbs, and bamboo...they seem to hold more and better fish, but require additional brush to be placed as they flatten out. PVC and other materials last much longer, but seem to hold less fish. Make sure to sink it deep enough so as not to become a boating hazard.