I've been noticing a lot of people in matches who are new and are getting their butts whooped. So I've made this post with tips that will help you understand the weapons.
Lancer - Default weapon. It shines in range next to the Sniper, not so much in close. Use it when trying to push the enemy team back and getting downs from far. Its meelee is the chainsaw which you hold the B button to rev it up. Simply walk into an enemy and watch the gore! A bit of a warning though, if you get hit while revving the Chainsaw, it will stun you, leaving you open, so don't run in a group of enemies head first with the Chainsaw. Another note, the animation is long, so an enemy can run up to you and kill you instantly while your chainsawing. You are invincible once you started the animation.
Shotgun aka Gnasher - Click left D-pad to select it. The shotgun is the first thing most players equip in a game, as most matches end up in shotgun battles. Obviously, the shotgun can rip an enemy to pieces if in close range. Note that all shots fired at random, so while it does aim on the body no matter what, there's a possibility that you can get a head shot with it. Its meelee is fast and leaves the enemy stunned. Line it up and fire, as a second meelee attack usually passes through the guy (thanks epic). I suggest equipping this first thing in the match, and pair up with a buddy. Also note that the shotgun CAN be used for long range, but only a few feet away will it actually down an enemy. The shotgun excels at close range.
Snub Pistol aka omg cheap weapon!!! - Click Down D-pad to select it. The pistol is fairly weak compared to other weapons, but its mostly used for a quick down. Its shots are DECENT, and can pick off an enemy already in the red, but don't shoot at a charging shotgunner! Its meelee is what makes this weapon so good, as the pistol's meelee is fast and brutal, only taking 2 swings to down a person. Use this weapon when the enemy is reloading, a weapon switch to confuse the enemy, and an annoying tool for bothering people with
Sniper aka Long Shot - Can be used only by picking it up. The sniper, as you all know, snipes. Learn it or don't use it, as it takes time and skill to master. The sniper is used to (duh) pick off enemies from a great distance. Its meelee is fast as well, and can down you in a second. Active reload it to down a person in one shot. And most of all, aim for the head! If your following an enemy using the scope and he rolls, he's a sitting duck. Ammo is 14 shots.
Boomshot aka Grenade Launcher - Can be used only by pick up. The Boom shot is EXTREMELY powerful, as a direct hit from it is instant death. But the deadly thing about the Boom shot is the splash damage. Most boom shotters aim at the feet in order for the explosion to colliode with you, downing or killing you. Best way to avoid this is keep dodging and rolling, don not run in front of the Boomer. Its meelee, like others, can down you in 2 shots. The ammo for the Boom is only 2 however, so use it wisely.
Torque Bow aka I couldn't think of a name - Only useable by pick up. The Torque bow can be charged and when lined up to the enemy, will stick to him and detonate, instant kill. If you do not charge it up before firing, it goes in a arc like pattern and does not stick on anything. If you do not shoot the weapon and hold the charge for a while, it will auto shoot for you, wasting ammo and time. Meelee is two shots as usual.
Hammer of Dawn aka Beep Beep Boom - Pick up only. The Hammer is also a charge shot. When fired, it summons a huge beam of energy down on the ground, destroying any person next to it. It will NOT kill them instantly if there a few feet away from the beam. You can move the beam as well to your liking. From what I've seen, the hammer will activate and start beeping when you hold the trigger and you are lining up next to an opponent. I could be wrong, but try it out for yourself. The meelee takes 3 shots to down a person and does not need ammo to fire.
Magnum aka useless - Pick up only. The Magnum, while useful in Single Player, is horrible on Live. It has almost no ammo, fires slow but powerful, and is a pain to find. 2 meelee shots will down a person. Stick to the Snub Pistol in my opinion.
Frag Grenades / Smoke Grenades - The grenades are powerful weapons. Press the left trigger to aim and line up a spot to throw it, and fire away. The smoke grenades are nothing special, just used to fog up an area. The Frag Grenedes are lethal however, as one blast can stun you if close or even kill you! Both grenades can be used to meelee, and both types stick to an enemy. The smoke meelee is used to humiliate or to fog up an enemies sight. The frag grenade "tag" sticks to an opponent, and explodes. If you are tagged, don't give up! Chase after the fragger and get him caught in the explosion! If you are the fragger, roll and run, as the enemy can give chase to you. If you have any questions feel free to ask or if I missed something tell me. I know its not the best tips but
Next topic will be multiplayer etiquette.