Here's a very handy link for explaining how tonight's games impact the Western Conference playoff ladder.
Basically, it lays out thusly:
If the Lakers win or Dallas loses, the Lakers are the West's two seed.
If both teams lose and Oklahoma City wins, the Lakers are No. 2, the Thunder move up to the three, and Dallas drops to the fourth spot.
Dallas losing means New Orleans wins -- they're playing each other, after all -- and a Hornets' victory locks them into the seventh seed. A Hornets loss combined with a win for Memphis against the Clippers at Staples leaves the Grizzlies in seventh, and drops New Orleans to eighth.
Portland, by the way, is locked into the sixth spot.
In a perfect purple-and-gold world, the Lakers would win, while Dallas, Oklahoma City and Memphis would all lose, leaving OKC as a four and New Orleans as a seven. More realistically, fans should be less concerned about what happens at the bottom of the bracket. The Hornets represent an easier draw for the Lakers, but if L.A. can't handle Memphis in the first round -- the Grizzlies, by the way, are fighting accusations of trying to tank their way into eighth -- they're not winning a title, anyway.
The big thing is keeping the Thunder on the other half of the bracket, meaning a win for the Mavs benefits the Lakers.
Assuming they beat Sacramento, that is, which given the context is hardly guaranteed. A loss to the Kings could very well leave the Lakers with a tougher first round opponent (Portland) and a second round series as the road team against Dallas.