Crouch when shooting. Aim at the head and don't hold your mouse. Click it every 1 second so your gun doesn't start bursting everywhere.
My Tips: Have a Small Crosshair. or keep trying with diffrent cross hairs at a CS:GO generator and see which best fits you. Ounce you found that. all you need to do is practice. Play with at easy mode first. then see how good you can get with your aim. its also nice to not have a crosshair too. and when you do get one you aim like a pro. Also. As Alex said. dont spam with your weapon. especailly if its a AK or M4
Joe is watching! BE AFRAID! Erm, more like move stop move stop. Move left, stop shoot, move right, stop shoot.
Only crouch at close or point blank range if your in a firefight. Doing it at long range just makes it easier for the enemy to headshot you. Check out The War Owl on youtube. His content is good and he does a lot of tutorials, and commentary on pro matches. https://www.youtube.com/user/TheWarOwl Also check out 3kliksphillip. https://www.youtube.com/user/3kliksphilip
Buy a bayonet fade then you will be better than all of NIP combined. You will be able to 1v5 clutch every round. Trust me.
Play with offline bots. Easy-Hard It trained me a lot. Also like people say above ^^ Crouching helps a lot. Also in Cod it helps too Also try starting out with the Deagle (Desert Eagle for Pistol) and that helped my aiming than before. Also it has a pretty good range.