As with any course of study, the more material you read on your own, the faster you'll learn and the more competent you'll be. There are many publications available from a multitude of sources, including most of the Glider ports. One such booklet that is stuffed full of information for a new or out of date glider pilot is the FAA “Glider Flying Handbook”, about $20. This small compact booklet contains all the theory and essentials of flight, soaring techniques, safety, navigation and meteorology, as well as many of the Federal Aviation Regulations. A good starting point or reference.
You will eventually need to know this material to pass the FAA written examination. You will be studying this material while you are taking your flying lessons.
Lessons can be scheduled at your convenience. The closer together the lessons are, the easier it is to build on the knowledge gained from previous lessons, and the faster you will learn. Most people try to fly at least once a week, and most prefer to take more than one flight during each lesson.
You can fly by yourself, "solo", as young as 14 years of age, but you can begin training as young as 12. No physical exam is required, but you must have no medical problems that would prevent safe glider operation. Typically, 30 to 50 glider flights, and some ground instruction are required to solo.
After you have passed your FAA written examination, your instructor will recommend you to take the Private Pilot Glider oral and flight test. Passing this test will entitle you to take passengers for rides.
The sailplane you will fly has dual flight controls, and your instructor will sit behind you. Your instructor has all the directional controls that you have and will show you the control motions or follow along with you as you are learning to guide the sailplane.
You will learn that a sailplane is a docile yet responsive machine that answers to gentle, coordinated pressures on its controls. You'll learn to fly the sailplane straight-and-level, to turn it in varying degrees of bank, and to recognize and recover from aerodynamic stalls. You will practice flight courtesy and safety, and will glide down to enter the airport traffic pattern at a predetermined altitude. You will fly your approach precisely, land your craft with its wings level, and stop where you want to stop.
Most instructors feel that 30 to 35 flights are the minimum needed for most people with no previous flight experience. An experienced power (airplane) pilot can generally solo a sailplane in less than 10 flights.