What are some things a beginner fly fisher should know?

Wow, this is a hugely broad question, even though you’ve provided some specifics. Without knowing where you are, what kind of fishing you’ll be doing, and how much you already know about fishing in general and fly fishing in particular, someone would be forced to write a book just to cover all your bases.

There are, however, lots of online resources for novice fly anglers. For example, here’s one:

This whole website is dedicated to introducing people to fly fishing, though I think even after reading all the content, you’ll still need some personal help and explanation. It’s a good place to begin, though. Here’s another:

This guy has centered his website around helping people get started with fly angling AND fly tying. Click on the “fly fishing 101″ side bar button and read the short articles he’s written on each topic. Some of the information is very simplistic and generalized, but it will help you become familiar with the basic equipment, terms, and techniques.

Though it might sound intimidating, one good place to learn about fly fishing is a fly shop. The clerks at a good fly shop will be happy to answer questions about rod size, line weight, the various tackle, flies, etc. Remember, they want more customers, and they want you to be interested in fly angling, so squeeze them for all the info you can get.

There are many, many other websites and online articles that will walk you through the basics of fly fishing. Once you understand more about it, maybe you could come back here and post some specific questions. Good luck to you — it’s a great sport.