The "Hitch" - my favorite
I have fished the "hitch" since 1964. I learned it from my guide Clifford House on Portland Creek, Newfoundland. He taught me to place 2 half hitches on the opposite side of the head just as described in Lee Wulff's book. He also instructed me to strike the moment I detected any movement in the vicinity of my waking fly. I have had lots of success with this method in many different rivers for Atlantic Salmon only. I have never fished for steelhead. Sometimes when changing to the other side of the river, I wouldn't bother to change the hitches to the other side of the fly head. It didn't seem to make any difference to the salmon.
After reading Art Lee's book on fishing the "hitch", I changed to placing the hitches on the near side of the head. He made the point that the position of the hook would pull into the corner of the jaw when the salmon turned to back into its lie, resulting in more successful hookups. I can't say I've lost fewer salmon since using Art's method, but his theory sounds good to me.
When to strike or not to strike the take is a question that depends upon the intent of the salmon and the nature of the water you are fishing. Usually in fast water the take is so fast you don't have time to strike, and in slower water the strike is more delibrate. Sometimes there is an explosion without any pull on your line. However, the advice to strike whenever you see movement near your fly does have merrit. I have found many times a salmon will take the fly straight on and not quickly turn. If you don't strike this take, you will probably end up with just a pricked fish. Depending upon the water conditions, quite often you will see the salmon open its mouth. You won't feel a thing, but I will guarentee the fly is in there. After a while, you seem to develop a sense of whether to strike or let it ride, just like in dry fly fishing.
The riffling hitch is my favorite way to fish for Atlantic Salmon; and other than the dry fly, is the most exiciting way to hook a salmon, much more so than just swinging a wet fly. My favorite patterns are Green Butt, Blue Charm and Thunder and Lightning tied in size 4, 6 and 8 on Tiemco #7989 light wire salmon/steelhead hooks.
P.S. Bill, I have taken salmon on the Dartmouth, York and St.-Jean rivers using the "hitch".