I also agree hook size makes a huge difference in keeping the fish on.

I fish from shore for salmon alot and at first i used 3/0 to 4/0 hooks. I lost alot of fish. An old man convinced me to use 0 and 1/0. He was so right.

I took this to the river and it worked well. I never go bigger than a size 2 and usually fish a 4 or 6 and rarely lose fish. I think it just doesn't tear them up as much.

As for the leader, like they say, probably the drag. It should be loose enough so the fish can tear off line easily when you first hook them. Then as they tire, gradually tighten it. Looseing fish can be very frustrating especially steelheading. Lots of time spent only to lose a fish really sucks the big one. Keep your tip up!