ghamorra is spot on. No matter how good your connection is if you have bad ping with the host then you will suffer. But there are things you can do to reduce the odds of that.
I've tried just about everything, but the biggest difference has been changing the primary and secondary DNS settings and reducing the MTU on both my router and PS3 settings.
I have a NAT Type 2 and am always open, and only occasionally suffer with any lag issues that I notice.
But, probably the single best bit of advice I can give you goes back to the beginning; avoiding a host whom you are likely to have bad ping with. To do that all you need to do is listen out for foreign voices in the lobby and back out when you hear them. It can be a pain sometimes, but I find it worth while.
Thanks for the feedback, I tried this also but am not satisfied enough with it, it means I have to back out like 20 lobbys before I can play.