There's actually a pretty good write-up on this site here
under the Omaha tab. The preflop strategy is especially helpful for newcomers.
The general rule of thumb is that you must play two cards from your hand and make the best five card hand. Since you have four to start with, all winning hands are going to be about twice as strong as Holdem. As such, don't be potting it with two pair on the river.
Opening hands should have at least two cards in the same suit, and double-suited (two cards in one suit, two cards in another) are good hands, espcially if you can get a high pair or connectors to give you straight and flush options.
I also find that playing Omaha gives me the extra benefit of being able to read my NLHE hands significantly faster.
GL out there!