I'm not a marvelous duelist or anything, but here are some of my observations after fighting with a two-handed weapon against another two-hander from versions .500 to .621:
Blocking. If you don't know how to manual block, don't buy two-handers in manual-block servers. Nothing is easier to beat than an attack-spammer with no shield. When your opponent blocks your first attack, you're going to die shortly after. That's if you even land your first blow: polearms are longer than your sword, and a fighter with a spear or glaive will take advantage of your ignorance. Be wary of feints, as blocking manually takes a wee bit longer than blocking with a shield or automatic. If your opponent feints once, don't think they're done playing tricks yet. If they see you switch your block direction they might feint again, especially with a faster weapon.
Length. Blocking hits is all well and good, but avoiding them entirely is better and leaves no room for error. If your weapon is longer (i.e. a two-handed sword against a two-handed axe) then you have an advantage you must keep. Many duels are short-lived due to one fighter swinging and coming up short while his opponent's swing connects. This is especially true for two-handed polearm usage. If your weapon is shorter than your opponent's, you must be relentless. Do not duck in and out of range, because that gives them the advantage. Stick close and don't give them room to maneuver or run away. Longer weapons tend to be slower.
Speed. Is your weapon faster? You better know how fast it is, because if you don't have length you need speed. Faster weapons are better for feinting, and a successful feint against an opponent gives you a free strike. That strike could be the only one necessary to bring down your opponent.
Wrapping. You can call it flanking or side-swiping or whatever you please, but I apply the term to shield-users and anyone else. Wrapping means to "wrap around" your opponent's block. It's the dirtiest trick you have against shielded opponents, but it can be used against skilled manual blockers as well. Essentially, if your opponent is facing you and they are directly in front of you, you cannot wrap. Your swing must start opposite from them. This sounds like a risky maneuver, and it definitely is, but if you fall into the block/attack rhythm this is the surest method of ending it. Before you begin your swing, you need to advance so that you are alongside them. If you are standing directly beside someone and their shield/block is facing opposite the direction you are facing, you turn towards them and swing. Your attack should strike them in the back, and if it does not kill them it should do enough damage to stagger them, opening them up for another blow or at least breaking the horrible block/attack rhythm.
god spear/shield is underused, it kicks ass)
