Your chiropractor will want to know which areas you are experiencing pain. They will want to know your medical background, your lifestyle (desk job vs building job) to determine the best method of treatment. It may be aggressive or more passive, depending on the ailment.
Your practitioner will ask you to remove your shoes and lay on the treatment bed. They may ask you to apply force against their hands to see how the muscle is functioning. They will then perform the corrective action known as an adjustment.
They will ask you to relax your body so allow them to perform the adjustment. They will then apply pressure to various areas of the body creating a cracking noise as the muscles and skeletal system realigns.
The noise can be a little disconcerting to begin with, but the key is to remain as relaxed as possible to allow your practitioner to realign the body.