How can I tell where the enemy is in COD to avoid getting shot?

Well, the best tip i could give you is check your minimap often. Its in the top right cornor and will show you enemys nearby based on where they have fired recently (unless they have a scilencer) Also if its advanced warfare you can see exo movement.

Use the minimap, check your corners, don't rush into open spaces, stay close to cover and know you're surroundings, in games like COD experience is key, which means that the longer you'll play, the better you'll become, eventually you're reflexes should also adjust to your sensetivity and your response time will get better.

Keep playing and find the playstyle that suits you, practice makes perfect, you'll get better as you play!

Firstly, The Art Of War is a philosophical treatise on grand warfare or "stratagem", meaning strategic, not operational or tactical warfare. There is information in it that will help you in many other situations (such as this), like the notion of strength and position. But it is not really what you should try to study for playing COD.

Secondly, COD is a pure videogame. Not really a realistic representation of tactical combat. Therefore only the very basic rules apply to the game.

These basic rules are the same for any simplified setting such as this... They are the same in Quake3 as in COD and they are quite simple. Since these are game rules we can liken COD to a shooting gallery game at the fair. Only it is a double ended one, where the targets can fire back at you.

Now, using this mental image, we can dissect what we need to master to win.

First, hitting the targets. This is about trajectory and speed. You need to learn the targets movement, how they move and at what speed. This way you can predict where they will go.

Second, range, learning to determine the range of a target

Third, threat assessment, figuring out IF a certain target is about to shoot you, or if it is likely to be just moving. Are the target in range to successfully target you? In the case of unseen targets, based on your experience are there likely to be hidden targets at this point in time? If so where? Now this is experience based, but the basics are the same for any game like this.

Fourth, making yourself harder to hit, if the targets are going to fire at you, make sure they have a hard time hitting you. This involves presenting a small hit area. So keep crouched, stay behind things and also run away to increase range, as in 3d space range makes you smaller to the attacker.

Fifth, movement, now use the above to position yourself so that you limit a targets ability to do the same. Meaning move to positions where targets may not use obstacles or range to limit their hit area size.

Sixth, situational awareness, look around you in 3d space all the time. Keep track of movement. Do not follow every moving target by moving towards it (remember, range) but register its trajectory in your mind, anticipate where it is going.

Seventh, keep moving. A moving target is harder to track down. Move in erratic patterns. Do unexpected things. This breaks the cycle that your targets will try to fit you to.

Most importantly - COD is a simple game, like most shooters. It is based on simple rules and reflexes and thus can be mastered like any simpler skill based game, with training. So training is key.