I read this thread thinking people were using some sort of seashell or the like and balancing it on the front sight, then I realized casing..
I did the coin and casing thing, but it didn't really help me much, similar to taking a person's breathing rate while they know you're watching, they usually breathe differently. I knew the gun was empty, and wasn't jerking down like I obviously was in livefire.
Personally it took seeing the gun jerking down due to a snap cap loaded in with the live rounds to hammer it in as to how fucked up what I was doing was. Knowing the extent of how bad my trigger jerk was is all it took for me to eventually stop that habit except when I'm practicing at speed, where all that stuff is fine as long as you find out what it is (shot calling, what you recall the grip pressure on your gun was during the drill etc.) and know how to, and work to stop doing it.
I will say that Ben's advice works in the way that I had to dryfire with the gun a bunch to know what a good trigger press feels like, double, single, what's acceptable on a far target, on a near target etc.
Occasionally during practice, especially when I get the feeling I'm starting to lose focus or am on autopilot I'll run a drill, then ULSC, then try to run the drill again but without having loaded a mag(But kind of not remembering it, even though I decided to ULSC). It still surprises me how often subconscious me jerks the gun down hard. Gets me focused again because I just hate seeing that shit.