[littlefileuser]

Although is cliche, I would probably do as the OP would: try to 'conquer the world.'

Although K's actual demeanor towards the Death Note was to justify peace and actually stability, as he stated, he really didn't think things through well and just went along with using the Death Note the obvious way: just killing off the people who did not go by his morals. He did not originally view the world as that, but eventually did.

For me, I would probably aim for world stability/peace as well, although maybe not be so rash about it, and try not to kill as many people as possible. I might die from Ryuk or whatever (as some of you have stated), but if my "figure/silhouette" lives on, I would be "alive" forever. Too lazy to explain my ideals.