Most Call of Duty gamers will not be fans of the tanks, though they can get players a serious number of kills due to their massive firepower and ridiculous armour. To take them out, Satchel Charges are the best bet. Either use them as remote-detonation mines (place them in the road and then detonate them as a tank comes past), or use smoke or sheer daring to plant them right next to the tank. Don't bother putting them on the shell of the tank as the weakest point of the vehicle is its underside. Failing that, put one on the back section. Anti-Tank Grenades are, as the name suggests, pretty effective in that they stick to the first thing they hit, making them ideal for long-range attacks on tanks from cover.
If you use these inaccurately you will have no chance of destroying a tank, as most players will only have a complement of one grenade. Stick it on the back of the tank or underneath it (you should be able to throw it pretty close to the underside) and you can get it in conjunction with a satchel charge nearby. Surprisingly, RPGs are not that effective and you will usually exhaust your ammunition for one life before the tank is destroyed. Having said that, aiming at the rear of the tank will dramatically increase your chances, but if you're going for any anti-tank class, Satchel Charges and Anti-Tank Grenades are the way to go. This video is from our unofficial game guide. You can view the full guide here
Added 7th Apr 2009, ID #800