Here's some photographic step by step instructions for tying the CDC emerger ~ black with Orange Butt. I find this fly very effective, its possibly the orange butt that gives the fish something to aim at.
Materials :-
Hook - Dry Fly
Thread - Black
Butt - Fluo Orange Floss
Body - Black Seals Fur, Hares Ear or Hare and Squirrel Mix
Rib - Fine Silver Wire
Thorax - Black Seals Fur, Hares Ear or Hare and Squirrel Mix
Feathers - 5 or 6 CDC Plumes (Less for a smaller hook)
CDC with Black and Orange Butt
Give it a try , great in size 10 down to 16 on stillwaters