A tick latches onto the skin by embedding its needle-like proboscis (the tick's "snout") into the underlying skin, where it creates a little pool for blood to accumulate. Finally, the tick releases some of its saliva — which may be infectious — to anesthetize the area and to thin the blood, and it begins to suck the blood.
The best way to prevent infection is to avoid places where ticks are most likely to be, which includes woods and high grasses, but also backyards and golf courses. Other measures include wearing light-colored clothing and covering as much skin as possible and applying a tick repellent containing DEET. Permethrin is another repellant that can be applied to clothing but not skin.
Finally, if you find an engorged tick on your skin, a single dose of antibiotics (doxycycline, 200 milligrams) within three days can dramatically reduce your chances of developing Lyme disease.
A vaccine to prevent Lyme Disease in humans is no longer available (though pets can still be vaccinated for the condition); repellants to keep your pets free of ticks can also reduce human exposure to infected ticks.