I ride fast and assertively, otherwise you get walked over. I don't hold traffic up though, and nor do I break the law - just sets a bad example.
If I need to be in a certain place on the road, then I'll take it (e.g. turning right). I'm not a big primary user as I'm not too bothered about close overtakes (used to riding close to other cyclists) but I ride a good secondary - 2-3 feet out to avoid grids, pot holes etc.
I don't respond to drivers, unless it's a 'WOW' if they make a mistake like not look or cut across the front of me.
To be honest, I'm far too busy riding the bike to be bothered to start tapping on windows or anything, even if they cut me up. The most I'll do is shout 'Wow' or 'Use your eyes' then carry on - just slows you up to much and buggers up the rhythm.
It's pretty pointless arguing with other road users as they usually get very aggressive - I tried to tell some spotty yoof that he was too close when he pulled out on me in a moped - got a 'poor response' from him. Had I been one the road bike, I would have just burnt him off, and embarrased the hell out of his pea shooter.
If someone starts 'beeping' I'll wave or wave the 'What' sign....
If out training (e.g. weekends) then I am very ascertive, but you have to be if you are going eye balls out and are concentrating on the job in hand.