I'm using the M16 with the ACOG at the moment, love it since the patch sorted the ACOG (previously used the red dot with the M16).
For run & gun, the MP5 is good (or, as mentioned, the P90 when you eventually get it).
Just keep playing. Get used to the weapons, & very important - get used to the maps. Know the layout, the good spots, what kind of style is best on each one. Do you run around like a maniac spraying bullets from an MP5, or do you act more carefully, shooting off short controlled bursts from an M16 (or single shots from whichever AR does those). Keep an eye on the radar, & watch out for helicopters!..
On 360, you can mute in two ways: Bring up the "Guide" (kind of like the "in-game XMB" the PS3 is hopefully getting soon), find the player & mute them. Or, use the new patch-added quick mute function. So, for the PS3, I guess the only way is via the patch's quick mute function.
Music... 'cos sadly many people on PSN (& XBL) are idiots & need to be muted. A lot of the time when I play, maybe half the people won't have their headset connected at all, & the other half just talk crap very loudly so end up muted.
ROFL
