One important thing is that you should be able to sit on a bike with both feet flat on the ground. This sometimes limits the choices for a girl if she's short (what we call 'inseam challenged'). Other than that, you want something smaller and lighter for your first bike. You don't want to buy a shiny new bike because you're going to be hard on your first bike, you're probably going to abuse the clutch, and you might drop it once or twice before you get the hang of it. Cruisers (like your BF's Harley) are easier to manage because they have such a low center of gravity. Plus they have a lower seat. Plus if you got, say a Japanese cruiser, you'd match your BF. Bikes like the Honda Shadow, Suzuki Savage, Yamaha Star etc. A 650 or 750 is big enough for starters, in fact you might not outgrow it at all. You should take the MSF course (Motorcycle Safety Foundation). They actually provide the bike for you. They will get you started with the right habits. At first it's all about safety, since half of all motorcycle accidents happen to people in their first year, so it's good to get started off on the right foot. You can find your local MSF through the DMV (or whatever initials they use where you live.) If you never rode a bicycle, I'd start with one of those to get the idea of balancing and steering. If you can't drive a car with a manual shift, it will take you a while to get the idea. But if you can ride a bike and shift a car, it's not hard to ride a motorcycle at all. And it's much more fun to drive than ride on the back!