PUBG is a battle royale game of 100 people on a huge map. Enemies can come from anywhere around you. If they see you before you see them, it's most likely that your game will be over unless they are a potato. But in PUBG, there is just too much space that you can't cover everything. Here are some of the few tips that will help you spot enemies easier in PUBG.
Graphics Settings
Screen Scale
Screen Scale will allow PUBG to customize the resolution of the game by percentage( 70 to 120) without interfering with the resolution of your monitor. By adjust Screen Scale to 120, the game will look much clearer.
Anti-Aliasing
Anti-Aliasing at low will cause the image to flicker, and our eyes will perceive the flickering environment as movements, thus making it harder to see real enemies.
Texture
Put this at Low or Very Low to see better contrast and the complex texture will distract your eyes from enemies
Shadow
Put Shadow at medium so you don't mistake the shadow for an enemy.
How to look
The easiest way to look for an enemy is to look for movements, especially horizontal movements. Next, you need to look for things or colors that are out of place, for example, a small black dot that is popping out of a tree could be an enemy is peaking at you or the shadow of a player standing on the roof. Muzzle flashes are also very helpful when you are being shot at from distance.
Where to look
Based on the plane path, the hot locations, and the circle, you can have an expectation of where people will go to and put more attention to that direction. If you are running to the center of the circle, you should keep your eyes on your sides and your back rather than your front. Also, prioritize dangerous places using clues such as open doors or dead bodies.