I am a native speaker and I just now realized that I basically never pronounce the 't' in words like 'hot'. Instead it sounds like a sort of semi-glottal stop. Is this common? How do you say it?
hot
I think this is extremely common in final t's. I myself do this very much so. There is no aspirated "h" sound to it and it is more of a, like you said, a semi-glottal stop if at all present. I live in a town called Butte and the way to tell is someone is from here is how they pronounce it. "Byoo" = native; "Byoot" = out-of-towner, ha, ha.
What I do for those final voiceless stops is I make the oral closure but with a simultaneous glottal closure. Well I don't know if it's actually simultaneous or not, but glottal closure definitely does occur, though you definitely CAN tell the difference between p, t, k codas. And yes, I believe this is common. Even in British English. Say "like that", but glottal-stop the [k], and give the [ai] a bit of rounding or backing. You sound British instantly!
What I do for those final voiceless stops is I make the oral closure but with a simultaneous glottal closure. Well I don't know if it's actually simultaneous or not, but glottal closure definitely does occur, though you definitely CAN tell the difference between p, t, k codas. And yes, I believe this is common. Even in British English. Say "like that", but glottal-stop the [k], and give the [ai] a bit of rounding or backing. You sound British instantly!