Um, specifically speaking - for my current relationship...
I was hospitalized for a stomach ulcer and anaemia after Xmas last year, my b.f. came to visit me and introduced himself to my parents - to my dad specifically. Dad just 'mmm'ed at everything he'd said and mum was fiddling with a plastic bag (dammit). They obviously didn't take him seriously. He gave me flowers the next day. Dad didn't say anything about it, avoiding the subject.
To this day, when my moble rings and I'm not around, he wouldn't tell me. Sometimes, like, when I folded 99 roses for Valentine's Day, he'd comment positively on my perserverance and skill...but you could just see his face sterning when I mention anything about the guy.
I know that dad's letting time to do all the work, to tell. So I can't bring anyone home yet. He always says that there's a time for everything and that right now I should study. I'm fully confident that my relationship will last and so at 21 or 22, I'd bring him home.
Otherwise, whenever I claim that I'm old enough for certain things, he'd comment on whether my bed's made in the mornings and whether I can tody and organise thigns properly. Very err...strict.