Boy Scouts can work on merit badges as soon as he joins a troop, but no merit badges are required for advancement until he receives his First Class rank. Advancement to Star, Life, and Eagle all require completion of merit badges. There are more than 130 merit badges.
Pick a Subject. Talk to your Scoutmaster or any Assistant Scoutmaster about your interest in earning a merit badge. Read the requirements of the merit badges you think might interest you. Choose one to earn. Your unit leader will give you a signed merit badge application (the "blue card") and the name and contact information of a merit badge counselor. Merit Badge Counselors have special knowledge in their merit badge subjects and are interested in helping you.
Contact the Merit Badge Counselor. Get in touch with the merit badge counselor and tell them that you want to earn the merit badge. The counselor may ask to meet you to explain what is expected and to start helping you complete the requirements. You should also discuss work that you have already started or possibly completed. You must always have another adult person present at each meeting with the Merit Badge Counselor.
Unless otherwise specified, work for a requirement can be started at any time. Ask your counselor to help you learn the things you need to know or do. You should obtain and read the merit badge pamphlet on the subject.
Show Your Stuff. When you are ready, call the counselor again to make an appointment. When you go take along the things you have made to meet the requirements. If they are too big to move, take pictures or have an adult tell in writing what you have done. The counselor will test you on each requirement to make sure you have done or can do the things required.
Requirements. You are expected to meet the requirements as they are stated. If you have already started working on a merit badge when a new edition of the pamphlet is introduced, you may continue to use the same merit badge pamphlet and fulfill the requirements therein to earn the badge. You do not need to start all over again with the new pamphlet and revised requirements.
Get the Badge. When you have met each requirement, the counselor will sign your application (the "blue card"). Give the signed application to your unit leader so that your merit badge emblem can be secured for you.
Following are the available merit badges, BSA updates the list from time to time, MeritBadge.org has helpful information including worksheets, and links related to each topic.
Eagle Requirement (Earn 21 merit badges)
Required Merit Badges: CAMPING, CITIZENSHIP IN THE COMMUNITY, CITIZENSHIP IN THE NATION, CITIZENSHIP IN THE WORLD, COMMUNICATION, COOKING, EMERGENCY PREPAREDNESS OR LIFESAVING, ENVIRONMENTAL SCIENCE OR SUSTAINABILITY, FIRST AID, CYCLING OR HIKING OR SWIMMING, PERSONAL MANAGEMENT, PERSONAL FITNESS, FAMILY LIFE. Plus 8 additional Merit Badges of your choice.