So let's start with basics. A tick is closely related to a spider and has 8 legs. Ticks suck blood from a host so it may start out quite small and swell to resemble a raisin, mole or lump on your skin. The most common ticks in North America I believe are dog ticks and deer ticks. You can learn more here. But what you probably came here to learn was:
HOW TO REMOVE A TICK
Many tricks can be used such as smothering them with soap, alcohol, burning them off (dangerous because you can burn yourself) and removal using tweezers.
Doctors recommend a simple 4 step removal process.
1. Grasp the tick as close to your skin as possible, preferably near it's head.
2. Pull the tick out slowly and carefully until it lets go.
3. Check that there are no parts left in the wound site (they feel hard under the skin). If there is something it will grow out on it's own or you can try to remove it.
4. Swab with alcohol and/or use polysporin cream to kill any bacteria in the wound.
Don't panic. While ticks are capable of spreading some diseases, notably Lyme disease and Rocky Mountain Spotted Fever in the US and Canada, they usually have to remain attached for 24-36 hours for this to happen so if you're out hiking just make sure to give yourself a quick check over every evening. Wear pants tucked into socks, long sleeves, avoid sandals and use bug repellant because many brands (containing 10-30% DEET) also deter ticks from biting. Not every tick you get on you will bite right away so try brushing them off. If you are concerned about a tick bite, remove the tick and place it in a jar of alcohol and then take it and yourself to the doctors office for a visit. Chances are you'll be fine though.