Hey Cheesehawk, more good questions.
1) I'm biking and see a snake streched across my lane. Do I just sit there and wait for it to get tired of sunbathing, or do I do anything to encourage movement (e.g. roll a rock), or do I pass it on the non-biting end, or none of the above?
Most snakes are on their way somewhere. So generally, slow down and stop 10 feet away and let them cross.
There are racers which will quickly be on their way, or the king snakes, rattlers or gophers will will move along at a slow pace sort of watching you as they head across the road. A rattler, long and low to the ground, has his tail up as he moves away.
If you need to pass quickly, say on a downhill at the last minute, yeah, head to pass at the tail end if you have enough space. 3 to 4 feet. A rattler must coil to lift to strike.
In the cooling nights, snakes do like to stretch across an asphalt pavement to warm their body in the dusk and dawn hours. Generally as you approach they will move along, give them a minute to see what their plans are. A rattler is most likely to respond with coiling if you disturb it. This is the perfect opportunity to cool your jets, observe the rattler in their magnificence, note the markings for looking up in your snake book later to identify it. Get out your flashlight, the light may be enough to move them off the road.
Rather than rolling a rock towards them, roll a rock or drop a rock next to you to make noise that is not directly pushing their buttons.
If it is a green racer, some may surprise the heck out of you and respond aggressively by coming after you!
It has been told of two legged quick exits!
2) I'm in camp and I hear the buzz. I look down and see a coiled snake three feet away. Do I freeze until it backs away, or do I leap backwards as quick as I can, or none of the above?
If you are in rattlesnake country, get into the habit of carrying a long 5 to 6 feet light weight thin stick.
Carried out in front of you low to the ground. Around corners where you can't see, you can lower the stick to the ground to make a scratching sound.
This stick has two functions. One, it will cause a nearby rattler that you may not or cannot see, to warn you of their presence before you step on it. Second, if the rattler is coiled and you are within range of striking, the end of the stick can be played in front of the snake's head and it will strike at the stick while you back away. Even better if you paint the end of the stick white. Or stick a little something on the end.
Most ratters strike two or three times, and they are worn out from their own response to fear.
If you must to kill it, let it strike the end of your stick a few times, then kill it with a shovel whack to the head. Easier said than done, as our responses to snakes are deeply engrained. You will also be in fear mode.
No need to kill any snake in the wild unless it is the midst of your camp.
A rattler dead can still strike and deliver poison. Pin the head down with a forked stick or shovel, cut the head off. Move the head with the shovel into a place where no one can have contact with it.
The body will still be moving, have "hiding" responses and will strike without the head. Wierd, eh?
All my information is from living in the desert in a remote region. Nothing official or scientific.
Truth is stranger than fiction or facts.