Pascal's Wager and the Heaven Lottery.

Pascal's Wager is a common argument, basically its that, from a game theory stance, you should believe in God because if there isn't a God neither belief or non-belief makes a difference, but if there is then belief in that God earns you an eternity in Heaven and non-belief earns you an eternity in Hell. Therefore, you should believe in God.

So first all you need to do is pick the right religion. So you have about one in a million shot (assuming the right religion has been invented yet) and if you manage to choose correctly (though you'll just choose your parents religion / how divine!), all you need to do then is trick God by paying apt enough lipservice.

If you hit the Heaven Lottery and pick the one in a million shot by guessing correct deity to feign belief in, you get to avoid hell! Though, any deity to whom this argument applies is evil. The concept of damning a person solely because of belief is the most abhorrent thing imaginable. Regardless of any good done by Gandhi, he's burning in hell. Norman Borlaug's Nobel Prize for saving the lives of about a billion people won't save him from hellfire and brimstone because he failed to stab true, while blind and in the dark, and feign enough interest to avoid the flames.

You might as well not bother. If there is an evil god who rewards and punishes on beliefs alone. Taking a stab in the dark is sure to fail. However, if there is a good God who rewards good actions, good intentions, goodness in people... then what does it matter what they believe? Furthermore, if there is no God, then you still get rewards as doing good is its own reward. On top of that a good God who rewards people for goodness might take offense to just guessing and feigning belief in whatever random choice you come across.

The only downside of doing good acts is that there might be some evil God ready to damn you for failing to choose it without evidence, among thousands of similar deities, and not also following through with some feigned belief upon threat of eternal punishment. -- In which case, it isn't a downside to your choice it's just a downside to everything.