Then work out a basic plan for on-bike communication. It's easy enough to speak with a passenger during around town riding, but it's tougher on the freeway, so work out a few basic hand signals; a pinch here or a tug there is usually enough to let the rider know the passenger's wishes. Make sure they've dressed appropriately. Then develop some simple rules: not jumping off/on the bike until the rider says so, don't put your feet down while moving, etc. The toughest job, of course, is the rider's.