I am the same as Phillip, usually hook in the middle, the logic being whatever end the fish start at the sooner they get the hook in the mouth however, it is always tricky with worms. I also used to like injected big lobworms with air, you don't hear much of that these days but it was the rage once; I had a lot of success on a reservoir once with that but I don't use worms much anymore, the odd one I dig up when fishing maybe. Mainly because eels love them and that's a problem on a lot of places I fish now. I didn't mind using a small hook with worms, just nicked through the skin half way along, a 14 or a 16 on a big lobworm. If the fish got it in its mouth it would be clear of the worm on the strike as it pulled through and catch the lip of the fish and they may not detect the hook so quickly with a small hook than a bigger one. At least I often found that happened but as I said I think it is always a bit tricky to get it right with worms. I think it is best to not be to rigid and experiment on the day, start with your favorite way and if your missing bites try something different. A lot will depend on the species and how they are taking the worm on the day.
The reservoir I used to throw in balls of groundbait laced with chopped worms, I had a place where I could dig a lot of them, they were orange because there was orange clay in the ground. I used to lob the balls just on a shelf about 3 rod lengths out, It was deep so a slider float was used, the air inject worms would pop up about 6 inches from the bottom shot, I had some good sessions with bream and tench mainly but the chopped worms would attract the Pike as well.
