It seems like a basic "New to Fly Fishing Guide" would be a great resource for folks getting into fly fishing. Here are a couple of things that I find important. Please add to the list if you have a good idea.
1. Don't go gear crazy. Start with a rod and reel or two and learn to use them. Only get new rods/reels when you find a specific need that your gear will not cover.
2. Fish with folks who catch fish. This is vitally important. You can either hire a guide, ask here for folks to fish with, or head to a river, talk to the folks who are catching fish and offer to buy them some beer for a bit of their time.
3. Go fishing. The more time you spend on the water, the more fish you will catch.
4. If fishing clear water, don't fish until you see fish. Once you can see fish, you can determine how much they are willing to move for food and what they are feeding on. 15 minutes watching fish will result in many, many more fish caught.
5. If you aren't catching fish, change tactics. This could include leader length, fly size/style, method and speed of retrieve, area of water being fished, etc...
6. Tie your own leaders and be able to make adjustments quickly. The leader is very important and the importance can't be overstated. Whatever method works for you will probably do the trick but understand and practice before you are on the water. This will save time and frustration. A good method for this is to pre-tie 10-12 tapered leaders @ home prior to hitting the water. If you leader isn't long enough, tie on another tippet section to your desired length.
7. Don't lose sight of the forest by staring at the trees. The primary purpose is to have fun. Getting too caught up in minute details detracts from the overall experience of fishing.
Essential gear: Good drag, polarized glasses, organizer for tackle/leaders, decent rain jacket, waders that don't leak very much, pliers or hemastat, and snips or scissors. There are many other things that come in handy but these are mandatory for most fishing situations.
Some of the more experienced members will hopefully add more comments.