By the time you get to the turn in pot-limit Omaha, you should have a fairly good idea what sort of range of hands your opponent(s) might be holding. While it is usually the case that multiple players either limp in or call a raise to see the flop in PLO, big bets on the flop generally tend to weed out the field somewhat, so oftentimes by the turn there are going to be either two or three players left vying for the pot.
Of course, just as the flop tends to change everything with regard to hand values, that turn card can also have the effect of altering the landscape significantly. For instance, that nut straight you flopped suddenly doesn’t seem to special when the turn pairs the board. Even a harmless-seeming flop with three different suits can suddenly turn sinister when the turn card brings a potential flush draw into the conversation.
The preflop and flop action should have given you at least some indication what you are up against when that turn card falls, although one of the trickier aspects of Omaha is the fact that since players are dealt four hole cards instead of two, the two cards a player might have been essentially ignoring on the flop can suddenly become very significant when a particular turn card falls, perhaps bringing a new draw or some other unforeseen development that changes players’ attitudes about whether or not to pursue their hands.
A key to deciding how to proceed on the turn is to become comfortable with reading board texture. The term “board texture” refers to how the community cards work with one another to provide hand-making possibilities. An uncoordinated board like 2h-9s-5d-Kc offers very little in the way of drawing opportunities, so if there is a lot of action on that turn king, you might well assume someone is betting his set of kings or perhaps two pair. However, a more coordinated board like Jd-Td-7c-8h suggests made straights and flush draws, and so it is prudent to proceed accordingly.
Another point to make with regard to turn play is the fact that this is the point in your PLO hand when it becomes vital to understand what the best possible hand is (the “nuts”) and to try your best to gauge whether someone else has it (if you don’t, that is). Because of all of the many possible hand combinations out there, it is probably safe to assume in most cases that someone has the nuts once you reach the turn, particularly if three or more players are still in the hand.
Thus if there is a pair on board, you should proceed with the assumption that someone has trips at least, and very likely a full house. Three suited cards by the turn also likely means someone has a flush, so don’t be stubborn about that straight you flopped.
