Example
Once you have balanced all the metals, now balance all the non-metals, except hydrogen and oxygen.
MgCl2 + NaOH ---> Mg(OH)2 + NaCl
1 Mg 1
2 Cl 1
1 Na 1
1 O 2
1 H 2
Balance the chlorine in the equation. It is the only non-metal besides hydrogen and chlorine. To balance the chlorine we can put a coefficent of 2 in front of the NaCl. You cannot add subscipts (ex: NaCl2). Remeber subscripts are from the charge of the element/ion.
MgCl2 + NaOH ---> Mg(OH)2 + 2NaCl
1 Mg 1
2 Cl 2
2 Na 1
1 O 2
1 H 2
Now the chlorine is balanced. The sodium is not balanced. At this point, don't worry we will take care of it in the next step.