For all you people who are having trouble leveling up, here is a trick you can use:
start a terrorist hunt game, select villa as your map, set enemies to high and difficulty to realistic, now for your weapons you must have C4 and frag, and a assault rifle and a smg a recommend the Famas with ether acog scope or the scope with the little laser dot (forgot its name) and mac11 with extended clip.
Once you start first place your team at the entry to your right, then place your self at the entry to your left, you will see an enemy behind the car kill him quietly using you famas, now leave your team behind and run to the stairs to your left but not up them, place a C4 on or near the stairs (explode when a group of terrorist are there), then through a frag grenade through the window above you, and run back the the garage and hide behind the wall, now most of the terrorist will come out to the front, so prepare for a fire fight, take out your mac 11 its perfect for this part, now you will notice the terrorist coming out, FIRE!!!, if you have left your team at the left entry point they should stop any terrorist trying to flank you. after the first wave you should have taken out half their force, now walk up the stairs and through a frag at the kitchen, then run back to the garage this should bring out the rest of the terrorist, if they all don't come out, get your team and enter through the kitchen and clear out the house there should only be 10 max.
rinse and repeat.
hope this help all you level up.