Find a bike, fall in love, and ride happily ever after.
Frame materials, geometry, and components differ on bikes designed for roads, daily commuting, long-range touring, or off-road riding.
With the right frame size, you should be able to extend your leg fully while pedaling, and should comfortably reach the handlebars. Riding the wrong size can be uncomfortable or painful over time.
Frame geometry has the greatest effect on how comfortable, efficient, and responsive a bike will be, but frame materials, wheels, and tires also play a role.
Once you've chosen a style of bike, you might want to think about the type of gearing and braking systems that will suit the places you ride.
Learn how to adjust your bike seat (saddle) to the proper height, angle, and tilt, for comfortable, injury-free riding.