North America has a few different types of poisonous snakes. The most likely places to find the rattlesnakes are in rocky areas, in piles of brush and even under tarps at your campsite. Copperheads prefer more grassy areas when they're not wandering into populated areas. And water moccasins are so named because they are found in water swamps, Everglades, streams and lakes. Copperheads and rattlesnakes usually communicate their presence.
Rattlesnakes shake their rattle and it sound very much like a loud baby rattle.
Copperheads give off a distinctive cucumber-like smell. Water moccasins are much more difficult to detect. They move silently and quickly. The same if you are walking through a field and begin to smell cucumbers. Take a few deep breaths and look around you without moving your head.