I'm going to go a little bit science.
Cumshot is a function of how much you have to shoot, the intensity with which you want to shoot it, the little muscles down there. And your biology. And if you are dehydrated. Or exhausted from lack of sleep.
And your body thinks that you should be pro-creating as soon as you are able to ejaculate (which on BW is 18) like when humans evolved, so the further you are from 18, the less fun it will be.
And if you came this afternoon, don't expect a big blast in the evening, and if you want one, then save up for a few days, or work on your kegels.
And of you really need to shoot, don't go out and get shit-faced or you won't even be able to get it up.
Put all of those things together - and maybe zinc glucomate if you want a chemical boost - which might work if you have low zinc. Or maybe order in someone who has an unusually tight orifice, or who simply turns you on more than anyone else.
You asked about the rules ... your body makes the rules. If you are young active and healthy your body will work well, and you will have mind-blowing orgasms and need to paint the wall behind your bed before you move out if you are jerking off. As you get older it needs more work, and there are a few physical things and some supplements that see, to help for a while. It's a combo of chemistry and mental. Be nice to your body and it will be nice to you.