On switchbacks you can often look farther up the road. So you can see how tight the next corner is. Most switchbacks are far enough apart that you can consider each corner separately. Picking the right line for an s-turn is trickier as sometimes you need to compromise one turn to be faster through the set.

Don't early apex. You'll go slower that way. I like to take a slightly late apex line because when I let off the brakes the bike accelerates. On entry use all of the road that you are allowed to use unless there's someone behind you that may take the inside and take your line away. I plan my line to give about 1 foot leeway on the exit in case there's something in the corner (sand, big bump, other rider) that causes me to change my line.

I try to pre-ride or drive courses so I know the descents.