Call of Duty 4: Modern Warfare/Multiplayer Strategies

General Tactics
These tactics can be used in almost every type of gameplay:
 * Watch the Radar - It can tell you where the enemy are, this gives you the chance to throw a grenade and prepare yourself or tell you which direction to go in.
 * Call in UAV while Sprinting - This means that you don't have to wait for the animation so you can react more quickly to enemy attacks.
 * Learn the Maps - One of the most important things to do, learn the hiding places and where to fire Airstrikes. This will help you a lot.
 * Stay close to walls - This means the enemy will have more trouble trying to hit you and you will be more camouflaged.
 * Move in the crouch position - This makes you less of a target and people can hear you less.
 * When going into open spaces, sprint - This makes you less of a target and may show you where enemies are. Try not to do this for too long.
 * Aim down your sights - This makes you a lot more accurate.

Free-for-all

 * Throw all of your Grenades and/or use your grenade launcher (for assault rifles) - You will die fairly quickly so this will get you a few more kills
 * Use Martyrdom or Last Stand (Perk 3) - These will get you more kills, especially martyrdom on the shipment map.