Do not use the minigun or other guns, including the snipers. Use the Kord 14.5 mm machinegun. Its damage is 700 and the weapon has more bullets than other snipers.
Shoot through walls
Get a weapon except for the MP5 or sidearm. Find a thin wall. Keep running into it and stay there. Your opponents cannot see you but you can see them and snipe them easily.
