This is probably the hippest my fingernails have ever been. Of course, there's a reason this photo is only of my left hand; the right hand fell victim to my poor left-hand motor skills and my impatience. They looked ok from far away, though.
I painted the whole nail gray first. Once it dried, I covered the bottom 2/3 or so with masking tape and then painted the teal on top, then took off the tape. Add a top coat, and ta da! You'll look way cooler than you are.