The net charge must be the same on each side one it has been balanced.
Don't forget to check your work to make certain the charge on both sides of the equation is also balanced.
A net charge is the charge of the atom after you know the number of protons and electrons.
If possible, start with an element found in one compound on each side of the equation.
Change the coefficients (the numbers in front of the compound or molecule) so that the number of atoms of the element is the same on each side of the equation.
Proceed until all elements have been balanced. It's easiest to leave elements found in pure form for last.
Once you have balanced one element, do the same thing with another element.