Three things 95% of Fortnite players don't do, and only the good ones do...do.
1. When you're in an open space and feel like you could get shot at any moment, start bunny hopping. You're 25% harder to hit and bunny hopping is relatively free to do.
2. When you get shot from someone out of your field of view, train yourself to whip the camera around and just start building walls while backing up. Once they stop shooting at you, build a ramp up behind one of your walls so you can peak them.
3. If you build a fort, everyone suspects it's occupied therefore you recieve unwanted attention. If you hide in a bush, you become the night. (There's a time and place for both)
Bonus: If you have a shot on an unsuspecting enemy remember to stop moving, crouch, and tap fire (do not hold trigger). You're a ton more accurate that way.