Sorry, I may have opened a can of worms and left the lid off. 6lb leader material seems to work best for me - just my choice. It's a little tricky tying on the really teeny flies (I need my glasses for those). It's definitely easier with a tapered leader. I used to tie my own tapered leader and there's lots of stuff on the internet on patterns for that, but even that seemed like a lot of work for nothing IMO - but some guys swear by it. Maybe I'm the lazy fly guy... My problem is I've left too many tippets in trees. Another thing is trimming tags. Some guys are real fussy on this, and how it should be done. So the fish can't see the line, but sees the tag? Well, to each their own I guess...
I think if a fly is presented properly, and it looks like food, and the fish is hungry - bang! Pretty simple IMO.