Mouse Sensitivity Configuration

There are multiple aspects when it comes to configuring your mouse sensitivity. By mouse sensitivity I don't mean the /sensitivity value, but the actual sensitivity of the mouse.
The true sensitivity of the mouse is best expresed with DEGREES / CM.
Like 360/10 which means that your ingame view would do a 360 degree turn by moving the mouse 10cm to either side.

True sensitivity = Degrees / CM

There are many variables which affects your true sensitivity:

Ingame sensitivity
Ingame Mouse Accel
OS Sensitivity
OS Mouse accel
Mouse DPI

There could also the settings on your mouse driver, but this usually is usually the same as / or overrides OS settings. For those unsure about the actual terms used here, read the small text below:

Mouse sensitivity is how far the mouse moves with a certain movement, should be pretty obvious.

Mouse acceleration (accel) means that the mouse will move more when it's moved quicker.
Lets say you set your ingame cl_mouseaccel to 0.5, then if you move your mouse really slow, you'll have about the same sensitivity as before, but if you move it fast you'll see that it acts as if you had a much higher sensitivity. It will move more the faster you move it.

DPI (Dots Per Inch) depends on your actual mouse. Normal mice has less than 1000 DPI (or even less than 500), while most gaming mice has over 2000 DPI. DPI is very important regarding the performance of the mouse.
With a high DPI the mouse 'engine' (laser\optical) will register your movements better and therefore be much more precise.

Configuring the true sensitivity

Basically, I'd recommend a HIGH DPI combined with lower ingame sensitivity. This means having an OS sensitivity that is comfortable for you to use at the desktop etc. And then configuring the ingame sensitivity (and possibly accel) to suit your ingame needs!

For trickjumping I personally prefer roughtly 360/10 as in the above example, aka 360 degrees by moving 10cm, and 180 by moving 5 cm.

360/10 is a somewhat high true sensitivity, but it's good for optimal allround control, and it's low enough to work well when you get used to it.
Having a lower one (like 200/10) would usually make trickjumping (gammas/strafepads at least) somewhat easier, but when doing jumps requiring more movement or other styles it would usually become harder.

Concerning ingame acceleration, a high acceleration (0.2-ish or above) is definately not recommended. Since this would make your mouse move a LOT more when moving quickly, it would give bad results when you suddenly have a reaction or suddenly move the mouse faster than you usually do.

When it comes to accel, if you're gonna use one, I'd recommend to set it to 0.05 or lower.
It could be a nice idea to set it to an ever lower value like 0.015 in case you'd want to get a little more 'snappy \ decisive' mouse movements.
The OS builtin acceleration could also be a useful replacement for this, but I have never tried it.

Mouse Hertz (Polling rate)

Mouse Hertz(Hz), aka polling rate, is the number of times the mouse reports to the computer every second. Or in other words the frequency (measured in hz) of which the mouse sends data to the computer.
The lower polling rate, the less lag between the mouse and the computer. Standard for most USB mice is 125 hz, which means an 8ms delay.
In other words, what happens on the computer screen will lag at least 0.008 seconds behind your actual mouse movements.

Polling Rate = 1000 / Hz
(1000 milliseconds / Input frequency (hz)

Obviously, the smaller this lag is, the better! The mouse movement will be slightly smoother and more responsive.
At some mice (Roccat Kone, Logitech G9, some razers?) you have mouse drivers / software in which you can adjust the polling rate, usually the options are 125, 500 and 1000. Possibly some more but not over 1000 (not that I've heard of).
There are also some software which can change this, but I won't go further into that.

1000 Hz would mean a 1ms delay, and 500 Hz would mean a 2ms delay. 1000 Hz might then seem as the logical choice, but at many mice (including at least the Roccat Kone) a polling rate of 1000 Hz is slightly unstable. I've tried it for a bit, and during that time I've experienced a few skips and a very fain negative accel. Not much, but enough to be make me go back to my normal 500 Hz.
I've used a polling rate of 500 Hz on the Logitech G9 too, and its just a 2ms delay, which is a 75% smaller delay than with normal mice.
So bottom line, I'd generally recommend a Polling Rate of 500 Hz, seeing as 1000 Hz might be unstable, if even just a tiny bit, it's not worth it. Better to be safe and stick to 500 Hz.

Below it's explained a little about mouse skipping and negative acceleration, which are two bad things you should do your best to avoid.

Mouse Skipping

Skipping means that the tracing of the mouse fails. In other words that it will suddenly skip from one position to another. This is in most cases caused by dirt at the mousepad, a hair in the laser/optical opening under the mouse?:P, and such things.
My old G9 mouse started skipping after about 2 years of heavy use. In retrospect I guess this COULD have been caused by some dust buildup further into the laser/optical entrance, or something related to that. But in either case I figured it was starting to wear out and threw it away, and bought the Steelseries Ikari, which as you can read below simply sucked. Now I'm currently living happily ever after with my Roccat Kone :)

Negative Acceleration

Neg Accel means that when moving your mouse quickly, it will move/accelerate in the opposite direction, or something along those lines. At least it will not move like it's supposed to.
This can have many reasons, most likely is that you got a mouse that can't handle it. However if you got a gaming mouse of some kind, there's a good chance it's something else!
Other reasons can be if you're using a low DPI with a higher sensitivity, or a low DPI at all. This increases the chances of neg accel.
Another reason could be the surface you're using your mouse on. Try some different ones, possibly buy a new different one or just try around a bit.. If this still doesn't work, and you got a decent DPI (e.g. over 1200) then there's a good chance your mouse sucks. I had a Steelseries Ikari Laser some time ago, and regardless of what settings or mousepad I tried (Tried 4-5 different ones, I could still get neg accel.

Some good mice on the other hand is Roccat Kone and Logitech G9, both of which I've used for trickjumping without any real issues at all. (Logitech G5, G7?, Mx518, as well I'd guess)
(Without any REAL issues meaning that the BUTTONS on the Kone is a bit messy, and the clicking function on the mousewheel is total shit. And that the .. small overlay thingy on one of the G9's 'covers' had almost completely worn off after 2 years of use, (started wearing off surprisingly fast, like after 4 months or so I'd say) having irritated me slightly on several occasions over that time.)