There are three general types of Omaha-8 games, fixed-limit, pot-limit, and no-limit. The advice given in this article is primarily for fixed-limit (also simply called limit) rather than for pot-limit or no-limit, but some of the ideas are applicable for pot-limit or no-limit.
Made Hands
There are 4 categories of made hands on the flop or turn:
1. Lows
2. Full houses and quads.
3. Flushes and straight flushes
4. Straights
One of these categories, #1, is for low hands and the other three categories, #2, #3, and #4, are for high hands.
How often is there a High/Low Split Pot?
There always is a high hand in Omaha-8. However, the board needs to have three, four, or five different ranks of low cards in order to enable a low.
The board only has at least three different ranks of low cards about three times in five (~60%). Even when there are at least three low ranks on the board, somebody still active needs two other low ranks to make a qualifying low hand.
In real play, someone often folds the only hand that would have qualified for low before the showdown. Thus, low actually occurs less often than 60%.
The percentage of the time low actually occurs is variable, depending on how those seated at the table play. 50% of the time is probably a reasonable ballpark estimation for how often the pot is split between high and low at a full table (nine or ten players).