Well, it depends, actually. If it's the Japanese version (in which, according to the show, says that *no one* goes to heaven or hell, which makes the concept of morality unnecessary) then I don't know what I'll do, as the shock of that revelation would make me go *insane*.
Now, if it was the American dub, which just has the simple "Don't use the Deathnote if you want to go to heaven or hell", then I would do the following.
1. Keep it in a safe place so no one could misuse it or accidentally screw themselves over by using it without knowing what it was.
2. If the owner asks for it, give it back. I wouldn't say anything about "trying not to let it fall into human hands" because he or she might think I was using sass against him and give him or her an excuse to kill me.
3. If the book no longer has an official owner, and the Shingami who dropped it says I should keep it, I'll try to befriend the Shingami. No really, I would. He could hang out with me, I'll let him has regular servings of his favorite human food and we could be best friends forever.
