This is a list of must have flies that will keep your creel full and insure many great days catching fish as opposed to just fishing for fish...
1. Parachute Adams
2. Royal Wulff
3. Humpy (and many of it's variations)
These dry flies are great to carry in your fly box. They don't imitate any particular insect, but rather fish see the fly as similar to what they are feeding on. These fly however will not work as great when fish begin to be vary selective. At that point you will have to do your work and match the hatch in both insect type and size. With the flies about it is important to match the hatch in the terms of size. This means that it is important to carry several sizes of each pattern. I like to keep a half dozen of 4 sizes of each.
5. Hare's Ear
6. Herl Nymph
7. Bead Head Nymph
Like the dry flies that I listed, these Nymphs work great at imitating a variety of bugs that may be in the water. I keep the same rule of half a dozen of each in 4 sizes.
Other Must Haves
8. Wooly Bugger
There are many variations of each of these fly types. There are some that are better than others and I have my favourites, but in my opinion as long as the fly does a good job of imitating what it is supposed to and in the case of terrestrials floats well with minimal floatant then they will serve their purpose. I keep several variations of each in my fly boxes as when one doesn't work than another might.
Remember to keep your fly lines wet and the inside of your waders dry. Remember to have a great time on the water.