Fishing from a tube is like fishing from a boat, only slower, and for trout that's a good thing. Here's a fairly current
Big Bear Lake Fishing Report that will give you some ideas about where to go and which techniques to try.
I fish from a tube every weekend and it's really all about the fishing. The tube is just where I'm sitting. Trout are tricky and Big Bear gets a lot of fishing pressure, so you're going to need to concentrate on good presentations and changing things up if you're not connecting. Good luck!