Start with a list of things you could not possibly be, or become. Things you don't associate yourself with normally, perhaps even contrary to your own nature. Rich? Sure, perhaps too easy, but what else? A planet, the tires on a Formula One Racer, a musketball in the pouch of a soldier during the Revolutionary War (choose your side), a barracuda, Roman Legionaire, Knight Templar (does this mean you know what happened to the gold?), bounty hunter, quasar or pick an element from the periodic table of elements.
Okay, now write a poem asking yourself what it would be like to be this thing. Or maybe go for broke and write it in the first person, as whatever you've chosen. Maybe you're just lying in the hammock in your backyard wondering what it would have been like if you'd just been born in a different century. Examine this new life, the possibilities and drawbacks. What is it you live for now? What keeps you awake at night?
Read Aimee Nezhukumatathil's poem Suppose You Were a Moray Eel over at Verse Daily. Get to work.