drops offs are the best places along channel edges . put them at lots of different depths so when the lake fluctuates you will still have good locations . the depths your fish like to hold at would be a great start and then deeper and shallower to allow for the ups and downs .
use hard wood if you can and it will be there longer . some hardwoods last a good while in the water . pvc is also a stay for ever thing . I know lots of folks that like old plastic lawn chairs too .