Couple of questions:
1) How do you deal with people who have shields as a 2H? Seems like they can just block your first hit and then your range advantage is lost right away. Then they just spam their faster attacks and either you block forever or you go for a hit and die.
2)How the hell do you kill cavalry? If I stand directly in front of them and try to thrust, I get run over. If I stand to the side and side swing, I hit their horse, but they usually kill me with the one swing.
Regarding your first question, the answer is proper movement (most people call it footwork). If you can find someone who is willing to give you some training on the duel server, ask him to show you how to turn into your swings and to help you point out errors in your movement and/or facing. Learning how to integrate movement into your offense and defense is as important as competent blocking when it comes to being successful at melee: it makes your attacks land faster, gives you more opportunities to attack, gives you more time to block, and is the only way to adequately defend against crushthrough weapons.
Once you get the hang of footwork, the fact that you will in most cases be much more nimble than the person with the shield (due to how heavy the shield is) combined with how your weapon is longer, usually faster, and has much better attack animations means that you can potentially be getting two attacks to the shielder's 1 attack if you are playing correctly. Unless he is good, you will have the initiative the whole time and force him to play very defensively.
Regarding your second question, it depends on the 2h you are using. A greatsword is actually one of the best weapons you can have against cavalry, due to the fact that it has incredible range on the thrust and will almost always hit the horse of the cavalryman before his heavy lance hits you if you aim for his horse's head. Basically, you want to thrust towards the horse's head while rotating/strafing/jumping out of the way of his counterattack.
If you do not have a greatsword, then you want to stand still right until he's in attack range and then strafe right or left while swinging at his horse's legs. Speed bonus works both ways, and even the most heavily armored horses are counted as having 0 armor on their legs. This means that 1 good hit to the legs with a 2h will kill the majority of horses in 1 shot if the rider was coming at you full tilt.