The premise is simple enough. God either exists or He does not. If you believe in Him and He exists, in the next life you will have infinite happiness. If you believe but He does not exist, or you do not believe and He does exist, or you do not believe and He does not exist, then you gain some non-infinite happiness in life. [Described more rigorously
here (pdf)]
As the math works out your expected value of believing is infinity, which means even if you are uncertain about the existence of God, you are better off believing (even if the probability He exists is extremely small). In the paper by Alex Tabarrok, linked above, Mr. Tabarrok makes an interesting offer. Let's say you are uncertain about God's existence and Alex comes along. He says, hey, I'll talk to God and help you get your foot in the door. According to the logic of Pascal's wager, not only should you take Alex's offer, but you should be willing to give him all your wealth for it... even if you think its possible that he doesn't really have pull with God (which he probably doesn't!). He is even kind enough to put his address at the bottom of the paper to recieve your checks! If it is hard to see why his argument works, and it was for me, read the paper... It is actually entertaining and really short.
The problem with all this talk surrounding Pascal's Wager is that the wager itself is weak. It rests on assumptions that are themselves uncertain. Why should we assume that belief in God, given He exists, will bring infinite utility (joy). Has he told you that? If you believe He has, then I would hope you also believe the other stuff He says to you too... which might help you understand the nature of belief.
For instance, perhaps you cannot believe just because you will it to be so. So even if you accept the wager, you cannot go from a state of unbelieving to believing. You need to believe in God first, to believe He can/will offer this eternal reward. If you think you don't need to believe first, then I might as well come up with Jeff's Wager which says I'll offer you infinite joy. Granted the probability is probably lower than in Pascal's Wager, you'd still have to accept it.
I think, help me figure this one out. Oh, and give me an equation to describe the nature of the universe. And I know I am taking a theoretical argument and trying to apply it to real life...