Much depends on the state in which you live. Go to your state's Bureau (or Department) of Motor Vehicles website; most of the information you're looking for should be there, including when the riding test is given (if your state has one), how many answers (or what percentage) you have to get right on the written test, etc.
In my state there is a written test for your M/C learner's permit, then a 30-day wait before you can take the ride test (on your own bike, we don't provide them). Also, as you're under 18 a parent or guardian will have to go with you to sign waivers (and possibly even financial responsibility papers) for you to take the ride test.
If your state offers the Motorcycle Safety Foundation Basic Rider Course, TAKE IT!! The course is designed to teach people who have never ridden a motorcycle how to ride; in my state, if you pass the BRC you don't have to take the state BMV ride test - you just take your learner's permit and your completion card from the course to the license branch and get the m/c endorsement on your license.
Among the advantages to taking the safety course is that it'll make your Mom feel better about her baby being out on a bike; the safety course provides the bike for you to learn on (usually a 250cc bike) and most can even loan you a helmet; and some insurance companies offer a type of "driver's ed" discount if you've passed the course.
The course costs money (in my state it's $75, in Tennessee it's over $300) and again, a parent or guardian will have to come with you to at least the first session to sign a waiver.
I am an MSF-certified safety course Instructor and a BMV Motorcycle Skills Test Examiner for my state.