Here one tip that I won't get killed for telling. It has helped land many salmon.

On cut plug herring, using slip tie. Pull the back hook so it is 3-4 inchs behind the bait. Many times the kings/springers(depending what country you are fishing) will swim behind the bait and nip the tail, and turn away. This puts the trailer right in the corner of their mouths. This works well for anchovy rigs also.