I'd be a mix of the 'tyrant' style and the 'good guy with a dark side' style. First I'd carefully study and memorize both the Art of War ( even though it might be considered cliched) and the Evil Overlord List before making my bid for power. Using the knowledge gleaned from the Evil Overlord List I'd begin enslaving the masses while appearing to be helping them. For example, I'd give everyone free unlimited (time wise) high-speed internet access, giving free (and good) universal health care, legalizing pot (and possibly other drugs) and eliminating the 'pay' part of pay-site porn. Then I'd slowly and methodically take over other countries and powers from the shadows.
After using that strategy to safely become the Supreme Overlord of Earth, I'd turn my scientists to discovering the key to immortality (free for myself and my trusted Lieutenants, and a small charge for the public) as well as fixing the planet/environment and possibly colonizing Venus, Mars and the Moon (to give to friends or family).