A routine check-up usually involves a cleaning and an examination of the teeth. Generally, your dentist will start by scraping off tartar (the hard build up on your teeth). The hygienist will then floss, polish and apply fluoride to your teeth.
Sometimes the dentist will want to take X-Rays while you are there. This process will usually take only a couple of minutes. First the doctor will give you a heavy apron to protect you from the X-rays. Then they will have you bit down on a piece of plastic, at which point they will take the x-ray. They may repeat this process several times to get a full image of your mouth.
The dentist may also decide to apply a sealant or fluoride treatment to your molars, in order to keep them from decaying.