From my understanding, the 3 top attributes for monks are...

1. Dexterity
2. Strength
3. Constitution

IIRC, each has it's own description in-game.  I am hoping to set up articles for topics like this in the Guides section.  But for now:

Dex influences: Critical hit chance, dodge chance, evade / resist chance, chance to defend and react to enemy abilities
Str influences: Un-mitigated non-critical melee DPS, increases weight at which you become encumbered
Con influences: Total hit points, increases resistances

~Kaji

That is a great runthru on which stats do what, however, make sure to read the top about the info being a tad old, the Racial stuff is different now, as is how softcaps/hardcaps are handled. While this doesn't change what stats you wan't to focus on, it might change your race choice