It's not an everyday thing for me because that would get old but if I'm really serious about her, I would definitely surprise her with her favorite flowers. That's also my style, since doing it on "special occasions" is nice but I think surprising her out of nowhere has more of an impact.
i would never send flowers. I might give them to her personally if we were dating and I thought she was super cool. but certainly not if I did something wrong...when girls do something wrong they usually just wait it out till you forgive them