Hey, nice to meet you
I wouldnt recommend using grenades to start with, but just for reference the fuse is about 6 seconds, and if you are still holding it when it gets to 6, I hope there are lots of enemies near by!
If you can bring down the console in game, its the button to the left of your "1" (I think this is the same on most keyboards). The scores that you get shown in Objective are pretty messed, the way I check to see who is alive/have i killed that guy? is by hitting /scores in the console.
also if you dont wanna annoy anyone, when you join a game hit /team auto in the console, then you wont teamstack on purpose
Watch the firemodes of your gun, the last thing you want is to let rip with your full automatic mp5 only to find that 1 shot comes out!!
That is all.