Might be a good idea to recognize a Cotton Mouth

[Wise Old Owl]

As you can tell from the foilage - we could not see the eyes as I was behind it... and it was off like a gun when I took the picture..

[sterling98]

I saw a snake today. Just a harmless black racer. It had a few big chicken eggs in it and was sitting in the coop starting to eat another one. The lumps disappeared when I picked it up with a stick and dropped it in a bucket (splat!).

[Kitecop]

All the poisonous snakes in the US, with the exception of the coral snake, have eliptical pupils like a cat. If it isn't a coral snake and it has round pupils it isn't poisonous. You may not want to get close enough to see the pupils however.

Almost all of them except the coral have keeled scales too, as do the water snakes.