Now days there are so many sniper manuals available online they are a bit redundant. The first time I read one of the manuals there are two aspects that make the most difference to a sniper’s survival.
1. Have a physical barrier between the sniper and the targets preventing direct assault on the position. A single sniper unsupported is easy to flank and or overwhelm.
2. Don’t use obvious spots like a ridge, stone out cropping or anything that looks like it could be used to hide a sniper. If you’re on a hill use the side of the hill in a ubiquitous location. Same with any other location.
Marine snipers during the Iraq invasion didn’t hide like they once did and used force protection with a squad. If you have guys with full auto and M203’s you might get away with this tactic.