Here's a couple of things i changed which helped a lot with aiming better and getting more kills. Try it if you want.
In the Game Settings there is 2 Crosshair options you can change:
1. Change your Crosshair Type to CLASSIC (old style CS crosshair)
2. Change your Crosshair from Dynamic to Static
Also another crosshair setting you can change:
3. In the console type "cl_crosshairsize 3" (5 is default, anything lower than 5 will make your crosshair smaller,2 & 3 are good options)
To get Net Info:
4. In console type net graph 3 (pick a number between 1-5 and decide which net graph you like more)
Changing rates will also help (like any other game), Net Graph give you some ideas of what Tick Rate some servers are running:
5. In console type "cl_cmdrate **" ( make ** either 64, 101 or 128 or find a number that works for you) some servers might restrict you
6. In console type "cl_updaterate **" (make it the same number as the one you picked in 5)
7. In console type "rate 30000"
Just changing these few things should help you guys getting a bit better hit reg ect, it's not illegal to change it

Play around with the settings in 6/7 but don't go to low.
Hope this helps a bit
