Updated June 15th, 2019.
You probably already know that ⌘-P brings up the Print dialog box. You probably also already know that pressing Enter (or Return) on the keyboard is the same as clicking the Print button (because it’s the default button, indicated by being blue).
Maybe you didn’t know that you don’t have to wait for the dialog box to appear on the screen before hitting Enter on the keyboard. You don’t even need to look! If you’re not going to change anything in the dialog box anyway, there’s no point in waiting for it to draw. Just hit ⌘-P, then Enter, as quickly as you can. Next thing you know, your page will come out of the printer.