[sniper caparzo]

I've always played free-for-all, but jumped into an objective based game the other day.

How do you plant explosives? I tried the usual action key that I use in single player and nothing happened. I couldn't find anything in the manual. Any help much appreciated.

Also, in spectator mode, how do you cycle through the players that you are watching? I've never done this before (unlike some dudes who do it to find snipers!) It would be handy to know so that I can snipe those damn spawn killers who appear to be everywhere these days!