Two more things that I find help that haven't been mentioned:
1- look for gaps in lanes, cos its more likely that other cars try to quickly change lanes into a gap, and they are pretty easy to spot.
2 - I usually hover my foot over the rear brake, just incase. Not had to use it yet
And don't be afraid to not filter! Sometimes you (or at least I) feel that you are "expected" to cos you are a biker and other bikers might be looking. Just slot in with the traffic if it all seems too hairy. I like Big Bad Al's philosophy, although I usually fliter at about 30 or so I think.