I would use a 7 or 8 weight fly rod if you are fishing for coho or other salmon off the beach. A 5 weight would be fine for cutthroat, which are a lot of fun, particularly if the coho are scarce.
As far as fly lines, you will get a range of suggested types. Personally, I tend to use an intermediate (clear) sinking line, often described as a monocore or slime line. If a particular beach has a very gradual slope, and is basically quite shallow, I would lean toward either a sink tip line, with the sinking section being that monocore type. These are called clear tip or ghost tip lines and because the rest of the line floats, your line does not end up dragging on the bottom during your retrieve.
In addition to the good information you will get fro members of this site, I would also recommend seeing if your local library has back issues of B.C. Outdoors magazines; some libraries carry the magazine, others do not. Going through back issues you will find many good articles on beach fly fishing which you might find useful in getting started.