The last 3 years I have hammered a heck of a lot of steelhead on both the swung fly and swung spoon.
I have tried a whole slough of things...
On the spinning gear I have tried everything from the side sweep, to having drag almost right off (using my finger to control line going out after the initial run), to letting fish set on themselves, to me hammering home on them. I personally found with spoons the best way about it was to absolutely hammer home - to the side. Straight up didn't produce good sets. Letting them take it didn't produce good sets.
Fly I have found similar. When I get a tight line hit, I let them pull my small 3 inch loop while my other hand reaches for the reel, and I hammer home. One smooth motion - first to the side that I'm swinging and then up. I miss next to no fish, and rarely lose more than 10%. One thing I want to stress here is make sure they have it. They don't hit flies as hard as spoons. I've never had a fish "peck" at a spoon, but I have had many do so at a fly. I never set on the pecks. Most of the time, my second swing through after a couple "pecks" will result in a solid stop - the stops are what you want to set on.
Lastly, dry flies are totally different. Best to keep your tip in the water, let them take, and literally don't do anything until you feel weight. Once you feel weight, do a strip set combined with a lifting motion straight up. Seems to work best for me after a lot of trial and error.