Red salmon are great fighters. They'll run, jump, and thrash wildly when hooked. They also are the least likely to bite. Fishing for red salmon in salt water is a waste of time. Even in fresh water, you often have to hit a red right in the face with your lure several times just to get it to bite. The good news is that what the reds are "in" they're often there in huge numbers of fish. Millions of red salmon come into Alaskan waters each year. As an example, the red salmon run in Bristol Bay for 1980 was estimated at 62.8 million fish.
By far the most popular spot to fish for reds is the Russian River where is flows into the Kenai. (The photo on the home page of this site is from a crowded section of the Kenai.) People line the banks of the Kenai where it meets the Russian. The area becomes very crowded when the reds are in, and this is where the term "combat fishing" truly applies. During red season, whenever I go by the Russian River area, I'll check to see if fish have entered the clearwater stream itself. If they're in the stream, they're often packed in shoulder to shoulder. I've limited out in minutes on some days, hooking a fish on every cast. The Kenai River is glacier fed and a cloudy green color, but in the stream you can actually see the fish, especially with polarized sun glasses. This means that you can make your casts to specific fish. And you can often find small groups of fish resting behind boulders or other obstructions.
When fishing for reds in the Kenai River, with its powerful flow of water, I'd recommend 20 pound line (as a minimum) on a medium to medium-heavy action rod. In the smaller streams, I normally use an 8.5 foot medium action rod with 12 pound line. I could go lighter, but if I can see that the fish aren't in the stream, I may have to move to the Kenai River itself, where the fast water would make a lighter setup impractical.
Because of the fishing regulations, the "Russian River Fly" (also called streamer fly or a coho fly) has become the standard for red fishing at the Russian River. These flies are available in all the local department and grocery stores. I'll use an 18-20 inch leader of brown 20-25 pound test Maxima line with a swivel on the top end, where my main line will attach, and a snap swivel on the bottom end, where the fly will be attached. A 1/2 oz. to 1 oz. rubber-core sinker is twisted onto the leader at the top end. (The regulations require the weight to be no closer than 18 inches to the fly.) Why use a leader at all? (1) I don't have to tie anything when I'm fishing, I just attach the leader to my line, and hook on a fly -- I can change flies, or leaders, in seconds, (2) I'll often handle the fish by grabbing this heavier line, (3) it's the part of the line that takes the most abuse, and (4) the fish don't seem to mind the extra hardware. Whether using a leader or not, attach the fly and put the rubber-core sinker at least 18 inches above it.
"Flippin": This is a useful method of fishing for reds. If you've spotted a fish, or group of fish, position yourself slightly upstream from them, ideally so that the fish are at about your rod tip's distance out into the water away from you. Strip out 6 to 9 feet of line from the reel. Hold the rod in one hand and the line in the other. Lob the fly out upstream allowing the cast to take out as much of the line as possible. As the fly hits the water, your rod tip is pointing at it. The fly will sink and be moved downstream in front of you. As the fly moves downstream, follow it with your rod tip, and pull on the line with your free hand to control the fly's movement and to keep the line tight enough to feel a strike. As the fly moves downstream past you, let out more line with your free hand. Then you can pick up on the fly by raising your rod tip and pulling on the line, to flip the fly upstream for another cast. (If this description is confusing, I'm sure you'll see other people doing this, and it's not a hard technique to pick up.)
As the fly is pushed downstream, you should feel your weight tap on the bottom. If you don't feel the occasional tap, add more weight. If the fly snags on the bottom, you can move your rod tip a little faster, or remove a little weight if it's dragging on the bottom. By practicing you can aim your fly's drift. You can control the fly's movement, both across and down current, by how you pull on the line and move your rod tip. The fly needs to be down just above the bottom. If it's even up at a red salmon's dorsal fin height, it won't bite. Some reds don't bite no matter how many times you put the fly in their face.
By drifting the fly downstream, and not pulling it quickly across the stream, you'll avoid snagging fish. I prefer using a long 8.5 foot rod so that I can reach out with the fly and not have to cast out and pull the fly across the path of the fish. I can float it down parallel to their path right into their faces. I've experimented in cases where I've found single fish resting in pools of slower moving water. It can take as many as 15-20 casts where the fly goes right by their mouth or right into their face before a red will finally bite.
Reds come in large numbers. When your fly drifts down into a large group, the fish you're aiming at might not bite, but his neighbor, or the fish behind him might. If reds are moving upstream quickly, they won't bite. When they're moving at a slower pace, in a group, or resting, they may bite a fly that comes into their strike zone. It's not as frustrating as it sounds because of the number of fish involved. If a single fish will only strike one out of fifteen times, a single cast that presents the fly to a number of fish may produce a strike; and some fish will bite at the first fly that comes by.