Hiding inside large bushes allows you to stay hidden while still being able to look around for threats, and even crouching inside small bushes can mask your appearance from all but the most eagle-eyed of opponents scanning in your direction.
You should never run straight across open areas unless you absolutely have to, as that's the easiest way to get spotted by an opponent, who can then either open fire on you or follow you and set a trap while you're unaware of the presence. Instead, hug the outside of buildings or move through trees to maintain as much cover as possible. Hiding inside large bushes allows you to stay hidden while still being able to look around for threats, and even crouching inside small bushes can mask your appearance from all but the most eagle-eyed of opponents scanning in your direction.