Avoid hardcore mode. Just makes it easier for muppets with machine guns to spray bullets whilst wildly shaking teh mouse back and forth to get one shot kills.
Hardcore mode is the only way to play, yes machine guns are a pain but I've had a hell of a lot more kills with my Deagle and one shot light rifle than I've ever had with a P90.
You can either put up with spray and pray loonies or you have to deal with a constantly on map showing where everyone is which, makes it far too god damn easy and the fact that you can put 4 or 5 bullets into someone's torso and they just keep coming.
At least in HC one shot can make a difference, you have to learn to react faster and aim better imho.