In Pai Gow Poker you are automatically disqualified if you do not separate your cards correctly so it is an important thing to get right.
Most casinos allow the player to have their cards set-up the house way which eliminates any sort of confusion.
Normally the cards themselves dictate the way they should be divided given that the five card hand has to be stronger then the two card one.
This is the common strategy for dividing the cards:
Nothing
Place set the second- and third-highest cards in your two-card hand.
One Pair
Place the pair in your five-card hand and put your two highest remaining cards in the two-card hand.
Two Pair
Either play the smaller pair in your two-card hand or play two pairs in your five-card hand.
The higher the pairs the more likely you should split them.
The smaller the pairs are the more likely you should play them together.
Three Pairs
Always play the highest pair in your two-card hand.
Three of a kind
Always play trips in your five-card hand unless they are Aces in which case you could split them up.
Straight
Your five card hand will be the straight.
Flush
Your five card hand will be the flush
Full House
Play the pair in your two-card hand and three of a kind in your five-card hand. Unless you have a spare Ace in which case you can play the full house as your five-card hand.
Two sets of Trips
Play the smaller three of a kind in your five-card hand and the smaller one as a pair in your two card-hand.
Four of a Kind
Split the four of a kind into two pairs with one in the five-card hand and one in the two card hard unless you have a spare Ace you could play in the two card hand.
Four of a Kind and a Pair/Trips
Play the highest of the pairs in the two-card hand and the quads in the five-card hand.
