First off, let's get the basics down. If everyone else was dead there would be noone to run the jobs like keeping electricity, food, and other things. Now that we have these things out of the way, I can answer. If I was the last person existing on this planet, I'd try to live as long as I could, doing my best to recreate the recources I commonly live with. I'd also search for other people still trying to survive. I'd get food and pray to god for help through my hard times.