First I'd start believing in God real quick.
Then I would bring world peace, stop hunger, crime and all that stuff; all the while either making sure that the earth can support the rise in population or making people procreate less.
Then I'd make my own life really comfortable I guess.
Oh, and I'd make it so that everyone were perfectly happy with their lives, find satisfaction and fulfilment, and as an added bonus they would get a tremendous intelligence.