I wouldn't say "accurately hit the weapon". It would be more like getting it in the way of the weapon, and given the size of most shields, accuracy is generally not a problem. Although there are points on the shield where the block would be more effective.
I have to disagree. I mean, yes, simply getting your shield in the way of a weapon is reasonably effective, it's a great way to break your shield. Much like a parry, the best way to use a shield is to strike the opponent's weapon out of the way with the *edge* of the shield -- rather than stopping the attack altogether, redirect it's force to the side so that it hits air, or the ground, as opposed to you. Effective plate armor works with the same principal.