There's always a trade-off when selecting a low or high DPI. Use what feels right to you. Do not feel that you have to play low DPI. The benefits are clear as day, but in practical terms everyone is different.
Personally I use 600 DPI (window 1280x832). I like it because I can still use only my arm if I want to, but I can also use only my wrist. Being able to change between which muscles I use gives me time to rest from muscle tension even while still playing. But this is completely my preference, so I'm not recommending it, I'm using it as an example.
As for polling rate. You should use the highest value your mouse can support, unless your mouse has bugs with certain values. Examples:
WMO has a higher perfect control speed on 500hz.
Some users of the G500 laser mouse have mentioned a major decrease in hardware acceleration when using 333hz. (Lasers pfft)
Experiment!
EDIT:
PhoenixBird wrote:
For pro mouses i think the best is to use 500Hz polling rate, coz 1000hz in usb 2.0 not supported well and it cut it...so then you play on mouse it feels like you fighting against the mouse(pulls the mouse). But for example on X7 A4tech polling rate 1000hz(in fact lower ~950 i think) so there is no cut of rate. For this type of mouse use 1000hz)
Just to clear up this myth. The bandwidth or polling rate regarding your USB port has nothing to do with your mouse cutting out. The bandwidth of even USB1.1 (12MB/s) is capable of far more than any mouse can send data at. Your USB controller is pretty much on holiday. The difference is how
frequently your mouse is requested to send data. All that matters is if your mouse can support it, and the drivers on your PC for your USB. That big fat image processing value you see advertised on your mouse is all done internally on the mouse, only the resultant counting data is sent to the computer, not the images.
Pancake wrote:
1000Hz should be the best polling rate if your PC manages to keep up.
Your PC can most definitely keep up. It's like holding a blade of grass in your hand and calling it heavy.