Remember that a player with no cards in his hand is Harmless, and cannot be the target of most cards, especially Weapons. Try to empty your hand so you are Harmless!
If another player is Harmless because he has no cards in hand, you can play a Tea Ceremony or Breathing card to make him draw one, so he becomes a target again!
Play your Properties! Their effects add together, and you can become very deadly with just a couple of Focus or Fast Draw cards. Plus, they take up space and are of little use when in your hand.
Beware of the Ronin! Especially with 6 or 7 players. Keep in mind that he triples his Honor Points. Try to spot your teammate(s) early so you can make an effective team.
Never let a player have too many Honor Points, unless you can truly trust him-which will happen very rarely! And keep an eye on anyone who plays a Daimyo to draw cards.
If you are the Ronin, you might disguise your Role by acting like a Ninja or Samurai from the beginning, trying to be consistent with your choice during the game.
Try to get the other players of the team you choose to be suspicious of each other, so they don't know who the Ronin is. At the very end of the game, you might Defeat a weak character, regardless of his Role, to get the precious Honor Points.
Justify your actions by talking, if necessary, especially if you are the Ronin. If you are convincing, you may befuddle the other players