I'm sure there is more complete info on what to do, but I know that staying calm and cool are very important. In short, don't go running down the trail yelling for help, that will get the venom moving faster which will cause damage to occur faster.

If you can summon help, it's best if you try to cool your body temp and stay still to slow down your heart rate and blood flow, and wait for help to arrive.

Put a splint on the limb that's been bitten and don't move it if possible.

Keep the bitten area below your heart.

I've read that if you can get into cold water that will help slow your blood flow, but I've also read that you don't want to wash the bite with water because residual venom on the outside of the bite can be used to identify the snake. If possible, I think I'd get in cold water if I knew what bit me.

If there is no help for you, put a splint on the bitten area and hike out slowly so you don't get your heart rate up.

Avoiding snakes is a good policy for backpacking solo. I try to be snake aware when I'm hiking. I check for them under fallen trees before I sit down on one, avoid piles of branches, check cracks and crevices before using them for a hand or foothold, and I alway use a flashlight at night to check for them where I'm walking.

In my experiences, I rarely saw snakes in the higher elevations of the Sierras, but saw lots of them in the foothills near rivers and creeks. Rattlers were easy to find in the Summer if you went looking for them. I lived in Castiac, CA for a while, that was said to have one of the highest densities of rattlers anywhere out there at the time, and I hiked the area extensively, but never saw one when I avoided snaky places.