If the communication was bad to begin with, chances are it will happen again given the opportunity. History has a funny way of repeating itself in relationships, and sometimes it's just not meant to be.
In saying that, if a guy wanted to re-establish the lines of communication with me, he just needs to pick the right time (ie: Not during office hours) and call me to talk to me about it. And if what he says shows me he is genuine and it's not a spare of the moment thing, he's really thought things through, then I would be likely to listen to him... And that's the first step.
If he was fairly sure I wouldn't want to speak to him, he could also write in a card or send a letter. I would be less likely to reply (Or pay much attention at all) to his contact if he sent me messages about it via SMS or even a email. I would likely be quick to hit the delete button and not bother with it. I would probably not appreciate flowers (Because I like to receive them in happy moments, not when there's problems involved). BUT when someone shows they are making a genuine effort to re-establish contact I'd be respectful enough to listen to what they have to say.
Hope this helps!