Ways to rank up faster in Battlefield Bad Company 2?

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I am currently level 8 (I don't play it that much), but I want to rank up because my friend has it and he's level 27. Is there anything I can do to rank up a couple levels a day like you can in Modern Warfare 2? Like is there a secret to it or something? Also, I don't know if this will help or not, but I use the second assault rifle unlocked with either a red dot sight or 4x Sight. I also use the sniper class with the m24 and a mortar strike with anti tank devices. So with that being said, is there any way at all I can rank up faster in Battlefield Bad Company 2?