The Flop

This is where you'll get a good idea where you stand and whether you want to push the pot with lots of raises or get the heck out of dodge.  There are some specific things you need to be looking for on the flop...

Are you drawing to the nuts? You had better be.

This is critical.  If you have a draw it needs to be to the nuts.  If you have a hand it had better be a nut hand. A mistake a lot of people playing Low Limit Omaha make is to draw to non nut hands--especially low hands. 

If you have 23 and the board is 678 and all you have going for you is that low then throw it away on the flop. You are drawing for (at best) only half the pot and you've got a low that is almost certainly beaten without an ace falling (4 outs).

Likewise if your main high draw is a flush draw then it had better be an Ace high flush draw.  Don't spend time chasing a King high or Queen high flush for high.  Save your money for a better spot!

Got Redraws?

When you have a good hand, like the nut low, and there are more cards to come you should be thinking about what redraws you have to other lows.  Having a dry A2 in your hand with the nut low is good, but having another redraw card is tremendously better.  Murphy's Law applies to Omaha as well and it will see like your Ace or Two comes on the river consistently to kill you without protection.

Dangerous Traps

I've flopped the nut straight on a board with a low

Here's something that comes up fairly frequently that many people play incorrectly.  Let's say the board is (on the flop):

Eight of Spades Six of Diamonds Seven of Diamonds

and your hand is

Nine of Spades Ten of Spades Ace of Diamonds King of Clubs
Hole Cards

you've flopped the nut straight and are on the dealer button.  By the time the betting gets to you it is capped already with five people in the hand.  What do you do?

Many people will stay in this hand until the end, but you should FOLD.  First, if you have a high hand only and a low exists on the board then you are usually (and in this case definitely) drawing to only half the pot, so the best case scenario is that at the end of all the betting you'll get half.  However a ten high straight is easily counterfeitable by the next two cards to come.  Any diamond gives someone a flush, a nine or ten gives someone a higher straight, and if the board pairs you are most likely losing to a full house or worse.  Even worse than that is the possibility that someone has a hand like:

Ten of Diamonds Nine of Diamonds Ace of Clubs Two of Clubs
Hole Cards

and is already taking half of your high hand in addition to the nut low.

Along those lines

More generally, if you have a high hand (no possibility of a low) and there is a low on the board then the high hand has to be incredibly strong.  If you don't have an almost absolute lock on the high hand after the next two cards come then you should let it go on the flop before you invest a lot of money in it.  Even when you have a strong high hand and there are two low cards on the flop you should be very careful, waiting until the turn to apply pressure if no additional low cards come.

Playing your low draws

If you have a low hand like A234 and only one low card appears on the flop then dump it unless you have a draw to a decent high as well (for example if your Ace was suited and two cards of that suit appear on the flop).

If you have a low hand like A234 and two low cards appear on the flop then pump it if you can. That is to say if your raises will not knock people out then raise.  This is where position comes into play. If you are last to act and seven people have already called a bet then they will most likely call your raise. The time to get money into the pot is before the river(!).  Once the last card is shown then it's usually very simple for your opponents to see if they are beat or not but before that card appears you can usually count on a lot of action at a Low Limit table.

If you flop the nut low then you should get money into the pot if you have low redraws. If the flop is:

Six of Diamonds Three of Clubs Eight of Spades

and you have

Ace of Hearts Two of Diamonds Four of Hearts Five of Clubs
Hole Cards

then you have a lock on the low (and a very good draw to a high hand).  Yes, get some money in there, however if your hand is:

Ace of Hearts King of Hearts Queen of Clubs Two of Diamonds
Hole Cards

then you should be much more cautious as any Ace or Two will destroy your low hand and if there is a LOT of action before the flop you may even consider dumping this hand as you are most likely facing one or more other A2's that probably have their own redraws to a low and you have no likely high hand appearing.

When the flop makes you very happy or very sad

Your hand is:

Ace of Clubs Two of Clubs Four of Diamonds King of Diamonds
Hole Cards

These flops make you very happy!

Seven of Clubs Four of Clubs King of Hearts

Yes, your hand is hardly unbeatable right now but you have excellent draws.  In most cases any club, king, four, or low card will get you at least half the pot.

Queen of Clubs Ten of Clubs Three of Clubs

You've flopped the nut flush so unless the board pairs you are almost certainly going to win (minus the very small percentage of the time a straight flush card falls like a Jack of clubs and someone has the eight and nine of clubs)

These flops make you very sad!

Ace of Hearts Two of Hearts Queen of Clubs

Yes you have two pair with Ace and Two, however you don't even have top two pair and there are several frightening draws out against you even if you do happen to be holding the best hand right now.  Any heart, King, Ten, or low card other than Ace and Two will most likely shatter your hopes of winning a portion of this pot. Get out now.

Seven of Clubs Seven of Diamonds Queen of Clubs

You have a flush draw with a pair on the board.  This is usually a bad hand to be involved in especially if you are up against more than one opponent.  Let it go.