We'll start with the perks:
Perk Slot 1
Bomb Squad: Detects explosives for you. Generally a useless perk, unless you get blown up a ton by "trap" explosives. Recommend using if you play Search and Destroy, or if you are a "stealth" style player, that frequently gets caught by claymores.
C4: gives you 2 charges that you set, and then detonate. Good for setting traps. Set up in chokepoints on high traffic maps to get 2-3 kills in 1 detonation.
Claymores: gives you 2 trip-activated mines. Great for campers. If you have that one sniper spot, or even if you're just using a long range assault rifle, set your claymores up at entrances to protect yourself from enemies trying to sneak up on you. Great perk if you don't run and gun.
RPG: gives you 2 missiles. Great for shooting down helicopters, but not very good at anything else. Hard to handle if trying to shoot at people, but can be used to blow up cars.
Special Grenades x3: gives you 3 special grenades instead of 1 (can't be used with smoke). Good if you are constantly rushing rooms. Throw a stun or flash into all the corners, then go in safe and knife or shoot the stunned enemies.
Frag x3: gives you 3 frag grenades. Great for maps where you might need that extra grenade. Grenade spam highly trafficked areas for easy kills.
Bandolier: gives you extra ammo for your primary weapon. Great for run-and-gunners that go a long time without dying. That extra ammo can be a great help. But this perk is usually best to skip with, and pick a more effective one from above because you can just pick up a gun off the ground.
Perk Slot 2
Juggernaut: gives you extra health. You can take plenty more hits and still be alive. Great perk for run-and-gunners. If you die constantly, try this perk.
Sleight of hand: reduces you're reload time by half. Useful if you consistently get killed while reloading.
Stopping power: increases your damage per shot. A shoe in for your pick of perks in slot 2. Kills people much faster than a gun without stopping power.
UAV Jammer: prevents you from showing up on the enemies radar when UAV is called in. Great to use with a silenced weapon and stealthing around behind enemy lines.
Sonic Boom: increased explosion radius and damage. Great with grenades, RPG's, claymores, or C4. You'll find yourself getting much more kills with explosives with this perk.
Overkill: allows you to carry 2 primary weapons. Great for snipers, or people who like to have a close range weapon, and a long range.
Double tap: increases the fire rate of your weapon. You can shoot a lot of bullets faster. Helps balance out weapons with a slower fire rate.
Perk Slot 3
Extreme Conditioning: allows you to sprint for a longer distance. Great for headquarters, domination, or search and destroy game modes. Also works good to cancel the heavier weights of LMG's, or to for an extremely fast class, go with a shotgun or SMG and be able to sprint for as long as possible.
Steady Aim: increases accuracy when not aiming down the sights. Great for CQC or players who like to "spray and pray."
Last Stand: after you are shot and would normally be dead, you drop to the ground, and have a chance with your pistol to take out any enemies close to you.
Deep Impact: weapons have greater penetration through walls. Great for lesser powered weapons when you need to shoot enemies through cover.
Dead Silence: your player does not make any noise (walking, etc). Great for stealth.
Iron Lungs: doubles the amount of time you can hold your breath with snipers. Highly recommended for anyone using a sniper rifle.
Eavesdrop: allows you to hear enemy team microphones. Generally a useless perk, unless you are playing an organized team on a private server that use mics.
Martydom: you drop a grenade when killed. One of the most hated perks in the game by others, but works great and gets kills.
Weapons Guide
Assault Rifles
M16A4: fires in 3 shot bursts. With stopping power this gun kills in one burst. Great rifle for hanging back and playing a medium to long-range game.
AK-47: full automatic with high damage. Great for short-medium range fighting. Requires more skill to fire long range.
G3: single fire shot. Great medium to long-range weapon. With stopping power kills in 3 shots. Low recoil lets you fire consecutive shots very quickly.
G36C: full automatic with good damage. Good for short to medium range, and can be pressed into long range service. Great damage compared to M4, but less recoil than AK-47.