In OA, this really depends on two things...
Rokugan or generic?
What focus are you going for?
I'll keep this as generic as possible.
1.) Your going for an excellent martial artist who can fight with or without weapons? Then select your bonus feats from the Dragon Style.
2.) Start as a samurai. Then alternate for a few levels. 3/3 is a good time to pick a focus (samurai or monk) or a PrC (Shintao monk is nice)
3.) Use bonus feats and swap monk feats to specialize in a fighting style (pg 80)
4.) Human is your best bet (feats). Spirit folk is a runner up. Any other race suffers Multi-classing penalties or is small (hurts monks)
5.) Try and think why two very different castes (nobles and monks) would be in the characters background. If you can't, try a fighter monk instead.