OK guys - this is where you help your fellow gamers survive and , yeah verily even advance, on Halo 2 multiplayer.
First, a shotgun at close range, sniper rifle, rocket launcher or the beam rifle can go right through your shield.
Having said that, probably the most important concept to understand in multiplayer is that you have a shield that protects you, unless someone shoots you (or grenades you). What does this mean? It means that you must usually be shot a couple of times to wear down your shield before you can be killed. And of course the same is true for your opponent. Your shield will constantly be depleted as you get shot or sustain grenade damage, and replenish as you do not. To kill someone, first you must deplete their shield. This is where grenades and dual weilding of weapons comes in. A grenade or a couple shots to take down the shield, one shot to kill, is probably the most effective scenario. But some weapons take multiple shots to weaken the shield, before you can kill with the same or an alternate weapon. (The plasma pistol takes only one charged shot, which can then be followed by the kill shot to the head.) Different weapons combinations are more or less effective.
This is why you shoot and shoot at them, then they seem to dispatch you with one shot. What is really happening is that you are merely weakening their shield without really hurting them, while they are blowing your shield away then killing you. This all happens very quickly while they are jumping around, turning, throwing a grenade or using their dual wielded weapons to deplete your shield, then getting off a clean shot.
A grenade can blow away your shield without you even realizing it, especially when three or four guys are throwing grenades at each other.. Then you are completely vulnerable. Run, jump or backup while vulnerable. Meanwhile you have to do something constuctive like throw a grenade at them, or shoot until their shield is depleted too, or run to a better weapon. Which brings me to my next most important concept...
Know the map with its default weapon locations
This is very important if you want to have a level playing field.
The other guys you are playing may have played Halo 1 multiplayer for hours and hours with their dormitory buddies on the same XBox split screen, or more likely, with the system link between multiple Xboxes! So they know some of the maps already, how to use the weapons against human competitors. They have lots of time to do all this instead of studying! Remeber they were doing this after you finally made it through the Maw on Legendary...
So to kill more that one or two newbies by chance in Rumble Pit, you need to quickly get to a powerful weapon on the map (shotgun, light sword, sniper rifle, plasma greandes), and you should know a couple of good escape routes for when someone is chasing you with a big gun. For example on the Lockout map, there is a shotgun in the green dead end hallway opposite the purple plasma elevator. How do you get it? By dropping down through the chute above the end of that hallway. But you have to know which chute is the right hole (the sword is at the bottom of another chute)...So go to that map though the system link menu - you can do that whenever you want - and run around on the map to learn it and find the weapons and escape routes.[/i]