In B&W you arrive at a land and on that land, you are born, as a god.
As a god there is noone holding you back. Do whatever you like. Who is going to stop you?
You can cause havoc, destroy houses, forests even lives, it doesn't matter. You're all powerfull, you can do anything you feel like.
But then again, perhaps you need more power or perhaps you're just feeling plain nice and want to pamper your villagers because they are the source of your power. In that case create houses, give them food and wood give them what they want and need.
Even though the way you treat your people is totally up to you there are certain consequences to every action you make. If you play evil, the people will think you're evil, you will look evil and even your temple will take an evil look. On the other hand if you play good and your villagers like you, you will begin to look heavenly good and along with you your temple will change you.
How evil or how good you are is determined by the amount of good/evil acts you have done and is measured by the game. It is called your alignment, an alignment of -1.00 is totally evil and an alignment of 1.00 means that you are totally good. So naturally 0.00 means that you are neutral.
So the choise is up to you:
Will you be a god who is good for his followers and will be worshipped because the people like and respect him
or will you be a god who finds no greater pleasere in torturing and sacrificing his villagers and that is being worshipped out of fear and anguish.
A big part of Black and White is about finding out your own alignment.
If you play the game for the first time just play it as you want, don't try to be good or bad just be what you find the most fun and see what your alignment gets
After you've played it ones you can try how it plays to become perfectly good or evil if you wish.
This is in principle the meaning of the game... where it not for your creature!
Of course no god can be truly powerfull without a worthy creature.
Creatures can reflect how you are, your alignment but also your power and greatness.
You can train a creature that does all the hard work for you like village managment and stuf, or one that impresses neutral villages, one that only goes out to destroy enemy villages or if you wish one that doesn't do anything else then dancing the whole day and makes friends with other gods creatures.
The choices are infinite.
Raising a creature is a lot harder then one might aspect especially seeing your a god.
You must teach them everything you want to know, that includes learning him important stuf like killing the people you want him to kill but also things that you wouldn't think of so easily like teaching him where, when and how often he must poop.
You have to take all this things in account to become a truly powerful god with an equally powerful creature but in the end... you shall succeed