Omaha Rules
Omaha poker is very similar to Holdem, with one exception. The betting is fast and fierce; this is why so many pros prefer Omaha over Holdem. You can watch many big name pros playing 200$/400$ Pot Limit Omaha at Full Tilt Poker. Names like Phil Ivey, John Juanda, Gus Hansen and David Benyaminne. Learn the Omaha Rules and you can master this game just like Holdem.
Just like Holdem, Omaha players must put in forced bets, otherwise known as the small blind and the big blind. The small blind is always half of the big blind, with rare exceptions, (.10/.25) for example.
Again, similar to Holdem, there are four rounds of betting. The most common form of Omaha is Pot Limit (you can bet only as much as the size of the Pot at any stage of the hand.)
In limit Omaha, the first two rounds of betting have to equal the size of the small blind. The final two rounds will be the Big Blind. For example, when playing 5$/10$ Omaha Hi, bets during the two first rounds have to be in increments of 5 dollars, and increments of 10 dollars during the last two rounds.

Step By Step Omaha Rules
1. The person to the left of the dealer puts out the small blind, and the person to the small blind's left puts in the Big Blind. (Any antes would have already been taken) Every player that's at the table is dealt four face-down "hole" cards.
2. The action is given to the person to the left of the Big Blind, who can fold, call, or raise. Each player gets a turn in a clockwise rotation, with the big blind going last.
3. Three cards are now dealt face up in the middle of the table. This is known as the flop, which is the first three of five community cards that all players can share. Now the first player to the dealer button's left, who's still in the hand, acts first.
4. After all remaining players have had their turn; a fourth community card is dealt face-up. This is called the turn, or Fourth Street. Another round of betting ensues.
5. Finally the last community card is dealt face-up. This is called the river, or Fifth Street. A final round of betting is done.
6. All remaining players that are still in the hand show their cards, and the best 5 card hand (using 2 hole cards, and 3 community cards), wins the pot.