Here's the only classes you're going to want to use..
SMGs - They're all good, but the easiest one to use is going to be the MTAR. Vector is strong, but it has terrible iron sights and a small clip. The second (my favorite) SMG worth using is the Bizon. It has a fast fire rate, which is awesome for close quarter maps. K7 has a built in silencer, so it's not bad with Grip+Ex Mags.
SMG Attachments - Grip (reduces weapon kick), Muzzle Brake (aka Long Barrel, which increases range, which reduces the damage drop off), Silencer (prevents you from showing up on the map as a red dot), and Extended Mags. I usually only use Grip+Muzzle, but Grip+Silencer should help you out since you're new.
ARs - SC2010, Remington, or Honey Badger. The remington has a small clip, but hits hard. It's kind of cheap, so I don't use it. I usually use the SC2010. The Honey Badger also has a built in silencer.
AR Attachments - Grip+Red Dot Sight
Shotguns - MTS or Bulldog. The MTS 1-shots a lot, plus you can shoot it as fast as you want, but it has a small clip, so you need to play smart. The bulldog has a larger clip, but it doesn't get as many 1-shots. The other shotguns are very flaky, plus you'll die if you get a hit marker.
Shotgun Attachments - Grip+Muzzle with MTS, and Grip+Ex Mags with Bulldog.
Snipers, LMGs, and Secondaries - Not worth using imo. People who use LMGs or Snipers are generally campers, plus I tend to avoid playing the shitty maps that benefit from them. Also, secondaries are very weak.
Perk Setup - The perks you'll want on every class are Ready Up, Focus, Dead Silence, Steady Aim, and Marathon. On smaller maps marathon isn't required, but it definitely helps on a majority of maps to flank, especially on the larger maps. Additional perks worth using are Agility for extra speed, and Sleight of Hand for faster reloading. Takedown is decent with the K7/Honey Badger too. Whatever you do, don't use Amplify. It instantly labels yourself as a bag of dicks. You won't get good at the game if you use Amplify.
Equipment - C4 or nothing. Some say C4 is cheap, but I don't think it's remotely overpowered. Don't use IEDs or Motion Sensors..unless you're a bag of dicks of course. Smoke is also nice for objective game modes.
Scorestreaks - IMS, Trinity, and Maniac are the only streaks I use. Satcam isn't too amazing. The dog is flaky, gives your position away, and makes it harder to hear the enemy.
Edit: Forgot to add tips..
Sensitivity - I don't remember the range that's on Ghosts. I think it's 1-20. I recommend playing on 4-6. The lower sensitivity will help your accuracy. At first when you're learning the maps you might get shot in the back, so it might seem like your sensitivity is too low. Once you learn the maps more you'll know where to look more, and be able to have better accuracy that others.
Button Layout - There's default and tactical. I recommend tactical. This means when you press down on your right joystick, then you'll crown or go prone. This works great in Ghosts.
What to do in a gunfight.. - You can either strafe (side step), jumpshot, dropshot, or knife. You can also ADS (aim down sights) or hip fire. You'll eventually learn to do what's best in any given situation. In closer quarters you don't always have to ADS, so hip firing helps. You can strafe hip fire or jumpshot/dropshot hip fire, which will help win a lot of gunfights. I wouldn't recommend knifing in ghosts too much. If someone is laying down, crouched, against a wall or corner, then they're hard to hit. Also, your knife stays in them in a while sometimes, which leaves you vulnerable.
Corners - Don't get caught sprinting around corners. When you come up to a door/corner, make sure you're not sprinting and be ready to shoot. If you're sprinting and the other person isn't, then it will take you more time to bring your gun up. Also, and this is very important.. you don't always have to go around a corner all the way. Sometimes it's beneficial to do a quick peak to check for people. Just walk out for a split second, back up, then move forward if the coast is clear.
Reloading - You don't always have to reload after you kill someone. Usually if you kill someone, then one of their teammates is going to come looking for you, so be ready to shoot again. Only reload when you know you're somewhat safe. Again, always be ready to react to the person who heard/saw you kill their teammate. If you killed someone, then expect someone to come to where you're at, especially if your weapon isn't silenced. A skull shows up on the map where you killed the person for the enemy team (unless they're using the Takedown perk).
This post was edited by ericswanson_19 on Nov 19 2014 03:34pm