call of duty modern warfare how to level up fast?
["Stick with a single weapon for the Mo' Money perk.", 'Choose your field upgrades wisely.', 'Stick to objective-based modes.', 'Shoot down enemy kill streaks.', 'Look for easy missions to complete.', 'Save your double XP tokens for later ranks.', 'Avoid special ops.', 'How to quickly level up weapons.']