ATC What is it? What should first time members in ATC do?

I am thinking about joining a squadron near my place, but I am not really sure about how it works. What should I do to join cadets and what are the fees? Is it on every day? And also what kind of activities can I take part in? Someone told me when joining the cadets you have to wear your school uniform. Is it necessary to buy other uniforms, shoes or boots? Please help me!!