You should try to keep sensitivity as low as possible such that you can easily kill 2 targets at 180
degrees from each other.

There are 3 main types of aiming:
Spraying:
You need to practice recoil patterns of most used guns using Recoil Master - Spray Training by Ulletical and then try to spray down several bots in aim_botz by Ulletical. Spraying is generally used for short range.
Bursting:
Bursting is the most effective aiming technique for short and mid range duels. For bursting you need to fire a burst of 3 bullets. Aim between head and neck, and burst to get an instant headshot.
Tapping:
It is used for long range fights mostly favorable for AK47 users due to its 1 shot headshot quality but you can use it with other weapons as well. In this technique you need to click the mouse for each bullet rather than holding it. You need to practice a lot to develop consistency in tapping.

"It is easier to kill STILL bots so here is an efficient way to kill moving targets:
There are 2 basic aiming techniques to kill moving targets:
Flicking:
You can practice Flicking via several community maps like aim_botz by Ulletical. For practicing
that you need to keep aim at one bot and try to flick the other one. You need to kill 150 bots
before every match by just flicking to develop a consistent aim.
Tracking:
You can practice Tracking via several community maps like Fast Aim / Reflex Training by yolokas.
For Tracking practice you need to aim at a particular bot and follow your aim with respect to
the bot movement. "DON'T KILL THE BOT JUST TRACK IT" Track about 80-100 bots daily you will develop consistency in tracking.
NOTE: Tracking is more consistent and reliable aiming technique you cannot rely on flicking every time.

You are inaccurate when you are moving, your shots will only hit if u are still at the time of shooting
and in order to be a difficult target movement is required.
Firstly, to become a difficult target only move sideways via left/right keys.
There are 2 main types of movement techniques:
Strafing:
In this technique you move then stop then move in the opposite direction but the main aspect of this
technique is that you need some time to stop completely and until your velocity is zero you will not
be accurate. BUT WE DO HAVE A SOLUTION FOR THIS:
Counter-Strafing:
It is similar to Strafing but you can stop faster just by pressing opposite movement key to stop quickly.
For example:
If you are pressing the "right key(D)" player model will move right, but when u want to stop you leave the right key and immediately press "left key(A)" and vice versa. This will definitely improve your aim since only
"DMGs and above ranked players use this technique".

If you want favorable aim duels you should keep your aim at head level and try to pre-aim common angles you might expect your enemy to be in. Peek when you are fully focused at your aim. To develop consistency in Crosshair placement practice prefire mode on Yprac Map Series by Yesber.
Holding an angle:
Whenever you are holding an angle donot stay there for a very long time. Try to peek and unpeek with 1.5 second gap using this technique you might catch your enemy offguard since he may have already cleared that angle.

Usually your hitbox should be head but if your opponent has his back turned then it will be difficult to hit a headshot so you should rather spray him down or use burst rather than tapping.

If you really use these techniques I can assure you that you will have sickest aim in the city.