In Pot Limit Omaha, players are dealt four cards, which gives each player a combination of six, two card hands.  In PLO, you want all six combinations to "work together".

A(h) A(c) J(h) T (c) is a perfect example of four cards that work together, and it is the second top starting hand PLO. Let's break it down.
1. First is the obvious pair of aces. 2. The A(h) and J(h) work together for the nut flush draw and nut straight draw. 3. A(h) T(c) work together for a straight. 4. A(c) and J(h) work together for a straight.  5. A(c) and T(c) work together for the nut flush draw and nut straigh draw.  6. J(h) and T(c) work together for a nut straight draw.

An example of cards that do not work together is K(h) K(c) 8(d) 3(s).  Let's break it down.
1. Wow, a pair of Kings to start.  But remember, THIS IS NOT HOLD'EM. It is highly unlikely that a pair of kings will hold up in this game.  2. K(h) 8(d).  No flush or straight draws here, just a king and an eight.  3. Same for K(h) 3(s); 4. K(c) 8(d); 5. K(c) 3(s) and 6. 8(d) 3(s).   So out of 6 possible combinations, only one, the pair of kings is working.  And the kings will beat by a pair of aces, which is likely to be out there in another player's hand.  THROW IT AWAY!

Another example of hands that do not work are three cards of the same denomination, like J(h) J(c) J(d) 3(s).  With this hand you only have a pair of jacks, no possible flush or straight draws.  One out of six combinations is a losing hand. THROW IT AWAY!  There are circumstances where a player dealt three aces or three kings might play, but that is a more advanced topic, not suited for discussion here. 

Then there is the hand with a "dangler".  This is a term coined by T.J. Cloutier which refers to a card that does not work with the other three cards in a starting hand.  An example of a hand with a dangler is are A(h) A(c) J(h) 6(d).  Let's break it down.   1. A pair of Aces.  2. A(h) J(h) work together for the nut flush draw and nut straight draw.  3. A(h) 6(d) is just ace high and will be beaten by any ace with a higher card, pairs, two pairs, etc..  4. A(c) and J(h) work together for the nut straight draw.  5. Again, A(c) 6(d) is beat by most hands.  6. J(h) 6(d) has no straight possibilities and is nothing more than jack high.  So out of six combinations, there are only three that work.  It's not a good place to start.  You are giving a 25% edge to your opponents from the start.  THROW IT AWAY!

So what are the best hands?  The top 20 hands are listed below:

1.  A-A-K-K double-suited (DS)
2.  A-A-J-T DS
3.  A-A-Q-Q DS
4.  A-A-J-J DS
5.  A-A-T-T DS
6.  A-A-9-9 DS
7.  A-A-x-x DS
8.  J-T-9-8 DS
9.  K-K-Q-Q DS
10. K-K-J-J DS
11. K-Q-J-T DS
12. K-K-T-T DS
13. K-K-A-Q DS
14. K-K-A-J DS
15. K-K-A-T DS
16. K-K-Q-J DS
17. K-K-Q-T DS
18. K-K-J-T DS
19. Q-Q-J-J DS
20. Q-Q-T-T DS

This is just a basic foundation for the types of hands to play in Pot Limit Omaha.  But obviously you do cannot wait around all day for one these hands.  Basic Pot Limit Omaha 3 will delve into the other hands that you can play.