Omaha Poker starting hands differ from Texas Holdem in that you are dealt 4, rather than 2 cards. When the best hand is made at showdown this comprises 2 (and only 2) from your hand and 3 from the 5 cards on the board. The best starting hands in Omaha poker are those in which the 4 hole-cards work together – giving you multiple ways to hit the flop.
Your 4 hole-cards in Omaha actually contain 6 combinations of the 2 cards that you will need to use in a showdown. A player is dealt cards A-B-C and D, the combinations are as follows A-B, A-C, A-D, B-C, B-D and C-D.
The best way to look at Omaha starting hands is to understand that all of your opponents have the same 6 combinations of the 2 showdown cards. You then work backwards to ask this question – what cards would I need to hold to maximize my chances against a number of players? This could mean 6, 12 or even 24 possible combinations against you.
What this large number of combinations means is that hole-cards with the potential to make straights and flushes go up in value, while those with only high-card value go down. On any one flop there are likely to be a combination of flush and straight draws, in a multi-way pot at least one opponent is likely to have a holding that works well with the board.
This is why the best starting hands in Omaha need to have cards which work together. For example 7-8-9-10 has the potential to make a lot of straights depending on the flop, while 3-4-9-10 can only make either the low or the mid-straight and may be vulnerable to higher straights in each case. Suited cards are also strong Omaha starting hands, these should preferably contain an ace of the same suit – giving you the potential to make the nut flush.
High-pair hands are valuable in Omaha, but are far superior when they contain other cards to work with. A holding of A-A-5-9 of 4 suits is really looking to flop an ace, any combination of flushes and straight draws on the board is likely to make continuing with the hand expensive. On the other hand A-A-10-J of 2 suits is a monster holding, not only do you have a strong pair, there are many flops which you could have a nut hand or strong draw to the nuts. A-A-J-10 where the A-J and A-10 combinations are suited is considered the strongest Omaha starting hand.
Starting hands in Omaha containing 2 pairs are also playable. You are looking to flop a set to continue in the hand and the chances of doing this with 2 pair are a little over 4/1. High pairs are again desirable, A-A-K-K (double suited) is another monster starting hand in Omaha poker. Beware of hands with small pairs, since you will face many combinations of hands at the table, bottom set might not be enough to win a showdown.
To summarize, the best Omaha starting hands are those in which the cards "work together" to fit with many flops. Connected cards and suited cards are both desirable as are high-pair hands where the other cards compliment the pair. 2 pair hands are playable but largely dependant on the strength of the higher pair.