An adjustment is a calculated force that moves the joint a few millimetres within its normal range of motion. Most chiropractors use their hands to provide adjustments and some use an instrument to perform the treatment such as an activator. Depending on the type of adjustment, your doctor will ask you to lay on your back, stomach, side or possibly remain in a seated position to receive the treatment.
If you have never experienced an adjustment before it is perfectly normal to feel nervous at first. Trust and confidence in your doctor are of the utmost importance, so make sure to ask as many questions as you require to feel comfortable. After your adjustment, you may feel some discomfort or fatigue but this should not last more than 24 hours.