If you are hiking or out in rattlesnake country, your best bet to avoid getting bit by a rattlesnake is to avoid them so much as possible. But if you find yourself in close quarters with a rattlesnake, it's useful to know that a rattlesnake can bite you from about a full length distance. So if you run across a 6 foot long rattle snake, they can get you from about 6 feet away.

Of course, leave as much extra room as possible :)