If you want a natural seating position, rather than straddling an engine, and to not be bothered with shifting gears, the flat foot-rest floor and convenience of an automatic transmission define you as a scooter candidate.
It's easier to master a motorcycle if you already know how to drive a stick shift.
Scooters and motorcycles can provide limited storage, but they are not prime choices for transporting passengers or much cargo. While long-distance travel can be a joy for expert riders, new riders are better served sticking closer to home. Short commutes and local riding are well suited to a neophyte, though consider the dangers that these rides may provide. Tackling rush hour in a major metropolitan area demands more concentration and experience than cruising through a small town or exploring scenic, rural roads.
Choosing a bike is often inspired by style and image, but these really should be secondary considerations. Don't pick a bike that's larger than you can handle. A standard rule is to choose a model that allows both your feet to be planted firmly on the ground when stopped, and beginners should be careful not to choose a bike that's too powerful for their ability. It is advised to start with a small-displacement model in the 250-500 cc range, although larger riders might be more comfortable toward the higher end of that scale, or even starting with a 700 cc, depending on confidence level and where they plan to ride. Following this strategy will lead you to a bike that will be satisfying in the long term. How can you possibly pick a bike you'd want to ride for years when you haven't even ridden for a week?
You'll also need a safe place to park your new ride. A garage is best, but bikes can be parked outside and covered. When parking outdoors, you'll want a secure location and/or a means to lock the bike to prevent theft.
Weather is much more of a consideration for riders than car drivers. You're literally out there in it, so be prepared to arrive wherever you're going wet, rumpled, or both, even with protective gear. And consider a short haircut, or "helmet head" will become your nickname.
Licensing is another consideration. No license is required for scooters with engines less than 50 cc in most states. You'll need to get a motorcycle license for anything larger than 50 cc, which involves a written and a road test. A list of licensing requirements can be found on the Motorcycle Safety Foundation (MSF) website.
Professional instruction and practice are a must before taking the test, and no new rider should take to the roads without lessons from a pro. Many classes provide entry-level bikes, giving a chance to not only learn, but to sample bikes before buying one.
Even if you're an experienced rider but haven't ridden in a while, a refresher course is a good idea. Classes are available for all skill levels.
Last, remember safety gear. You'll need to invest in a helmet, gloves, and other protective clothing. In addition to protecting you in a crash, the right gear will help shield you from the elements.