Essential ingrediants:
1. Good salted herring with all the scales still on and clear eyes.
http://www.salmonuniversity.com/ol_brining_herring.html2. Good herring threader with a tip that the loop on your threading leader and hook fit into.
Some come with a nice flattened section about 2" in which is nice for filleting the tail end.
I had a partner whine for hours when his deckhand threw his "favorite" overboard so you should have several.
3. Your favorite bait hook on a 28-72" leader with a loop on the flasher end.
4. Take your herring and stick the threading needle in the vent and fillet the tail. After a while you fillet the tail and remove it in almost the same motion.
5. Carefully slip the threader through the vent, through the body cavity, through the gills and out the mouth. Put the threader in a secure spot.
6. Carefully pull the leader through the herring and position the hook so it fits securely into the body of the herring with the hook, single or treble, coming out of the vent facing downward. I usually have either treble or single hooks with an anchoring barb or stiff wire to slip into the backbone.
7. Take your noseclip and securely fasten it to the chin of the herring over the mouth and nose.
Here is a good primer on rigging a cut plug if you are using rods. When using rods commercially I went to rolling whole herring as they hold up better than cut plugs.
Anyway this is what I do. But I am not a great herring fishermen as I made a living trolling from 1982- 2000 without ever running bait.