As a quick reference, if the snake has a flat triangular head, keep away, it may be venomous. If the head is rounded, it is most likely non-venomous. We have lots of snakes around here--rat snakes in the barn are more than welcome since they help keep the rodent population down; prairie king snakes, who also are beneficial and just so darned pretty; and near the pond we have cottonmouths and a few rattlers that we respect and stay away from. Most venomous snake bites are "dry" which means the venom is not injected. After injecting venom, the snake has to build up a store of venom and is pretty helpless during this time.
Snakes don't hear, but they are very sensitive to motion, so we wear boots and walk heavily. The snakes feel us coming and go away.
If you want to learn more about Texas snakes, I recommend Texas Snakes by Werler and Dixon. It's a hefty tome but has great descriptions, photos, and facts.
Can you tell I like snakes? They are pure muscle, very efficient at what they do, and are pretty, too. Think of them as the movie stars of the reptile world!