Here is what I know about aiming
Lowering your sensitivity is in most cases a very efficient way to improve aim (and you don't have to buy a new mouse with 2000dpi with a low sensitivity. Keep your old one

HIGH sens needs high dpi!)
There are two ways for aiming (with mouse of course, maybe there are people who use a joystick, touchpad or touchscreen

). You can use your wrist or the whole arm. I have asked many players how many centimeters they need to do one turn in nexuiz to get more experience.
Armaimers seem to have about 30-40cm / 360degree (I know only one player with 40cm thats kojak

)
Wristaimer are around 15cm / 360degree
But there are some very weird exceptions:
Most of us who play minsta know pat. He told me he is a wrist aimer, has about 30cm/360 and fov 90 (it was 80 in the 2.3 times iirc). I have no idea how he can play with these settings. But this nonstop zoom and extreme low sensitivity seem to work, even without moving the whole arm.
Another exception is Bundy. A 1on1 player and 6cm/360. As 1on1 player your fov is usually somewhere around 120. (His mouse has 2000dpi. as i already said: "high sens -> high dpi")
My aim has become a lot better after lowering my sensitivity (from 2cm/360 to about 16cm/360

) but i'm not satisfied with it. Compared to those guys above my aim is still terrible weak.
The last thing I want to mention are reflexshots (or flickshots, thats how bundy calls them). In some situations in the game, you just move your mouse as fast as you can and press fire. Somehow these shots are hitting surprisingly often. The more normal way would be moving your crosshair with your mouse onto your target (no strafing). This is where I have some question myself.
Which is the best way to aim?
1. Doing hectic reflexshots and wild mouse movements as much as possible?
2. Trying to aim like a aimbot, so that your crosshair is always on your target?
3. Wait (which maybe hard in a battle) untill your target moves onto your crosshair?
Atm I'm doing mostly 1. Sometimes 2.
Somehow 3. doesn't feel like aiming to me. But I suppose 3. is the best method, even if it feels very ugly.
Any suggestions how to get advanced aim?