The lights are on
Ok here are some tips for beating Killzone 3 Story mode(any difficulty mode) and multiplayer. It's only a matter of following these 6 easy steps:
1) In Story mode always let your partner do most of the work. Just let him do the dirty work since he's never gonna run out or ammo or die. If he gets wounded just help him by healing his wounds. If you are alone, protect every soldier that you see. In multiplayer always aim for the middle part of the torso. It might sound stupid but shooting your enemy in the nuts can really damage them. If you don't want that simply just shot them in the back. Apparently it creates more damage.
2) Always but ALWAYS keep a long distance. Try to learn how to use the long distance weapons.
3) Grenades become your best friends. Take your time. Don't throw it until it's about to explode, that way enemies won't be able to cover. This is one of the best tips at multiplayer.
5) If you are attacking multiple enemies at the same time try to take them out in a single hit with a weapon that has either lots of bullets or a huge damage radius like the shot gun. If you only have a few enemies and they are scattered around the map, run and use a fast melee attack.
6) THIS IS THE MOST IMPORTANT TIP! have fun, at the end is just a simple game, try to play with your friends. Remember that you can always become better.
Well I don't know if these tips are gonna work you but the work for me.