>I want to not suck.

Ok.

>How do I kill lots a people and raise my k/d?

Drop in high population areas and look for fights immediately, you will die a lot at first but it's quick and you'll learn how to outplay people and your aim will improve. Shoot quickly with semi-automatic weapons, this will get you used to aiming and clicking quickly at the same time.

>How do I not have a panic attack when someone starts shooting me and I don't know where from?

Do the above, get yourself comfortable with taking fights. You must understand how to play methodically. As for not knowing where you are getting shot from; turn up your volume, use headphones, listen only to the game. (if you right click your sound icon on your task bar and see if there is a spatial sound option. enable it.) The first thing you need to rely on is echolocation, you can hear which direction shots are coming from. Once you get a general bearing of where the shooter is, get to the nearest piece of cover between you and them. Finding a 4x is necessary, once you reach cover, lean peak out quickly and aim at pieces of cover the shooter is likely behind in an attempt to spot them, you can tell how far away they are depending on what you hear from their shots. Shots from a long distance will sound after the round has already hit you (as bullets travel faster than the speed of sound). When you get hit don't panic and listen for the thud of the shot in the distance, you can hear where it is coming roughly and then you do as described.

>How do I prevent myself from being in a bad position in the top 20s and top 10s so I don't get picked off by being in plain sight?

Think about where you can be seen from, the less angles that you can be spotted by the better. For example, don't run on the crest of a hill, run just below it on the side of the hill so you can only be seen from one side. The side depends on where you're less likely to be spotted. When running across a field always run from cover to cover, from tree to tree, or hay bale. You'll be far easier to spot in a field so it is good to always have nearby cover in the event that someone starts shooting at you. Use terrain to your advantage, read up on hull-down (https://en.wikipedia.org/wiki/Hull-down).

>Should I be aiming for the head most of the time, unless a headshot will be very unlikely to hit for some reason and bodyshots would be better?

It all depends on the situation you're in, if someone is running straight towards you or directly away from you at short to medium distances, the head shot would be a relatively easy shot, and a quick frag before your opponent can shoot you back. With a level 2 helmet and above you will need 2 or 3 head shots to kill someone depending on your gun, a good way to kill is to shoot the head once and then aim for body shots until they are killed. If you have sniper and an automatic weapon and you land a head shot at close to medium range you can swap to your automatic weapon to finish the enemy quickly with a spray down. At long ranges just try to hit them, period.  Don't stockpile ammunition, leave room for a lot of meds. You will win a lot of firefights, especially later game, that results in you getting hit a few times and therefore low health, use a first aid kit and an energy drink to bring you back to full health if you're low. If you're around half and above use one painkiller and one energy drink to max out your  boost meter and you will heal over time and you increased speed will make you a harder target to hit and will also allow you to reach cover faster in the event that someone else engages you. Stay boosted late game when firefights are frequent, the healing it gives you will increase your survivability in combat. Think of it as damage reduction.

>How do I spray and pray with the AKM?

Find an AKM and some ammo, put it on full auto, find a wall, aim down sights, and hold down shoot. This will give you a general idea where the bullets go at certain distances, counteract the pattern with mouse movements, drag down as you shoot.

>Please respond.