How can you tell if you are in an area that has caddis pupa or larva if you see no visible signs of adults? I do this by scanning the shallows and looking for their rock-like casings, as I find these the easiest to spot.
The picture below is what you need to be looking for along the streambed to determine the presence of caddis.
As far as tying these patterns, there is a huge range of possibilities. I have seen some that involve nothing more than some rubber ribbing, dubbing, and a small black bead. Others have ranged from CDC feathers to improve swimming action to leather strapping to simulate body texture and color. The choices are limitless. The most important fact is that you have to use what works best for you and keep casting.
My Simple Caddis Pupa -
Here is a more complex version that I started tying this weekend - Charlie's Caddistrophic Pupa