Final answer:
The first rule of thumb for balancing chemical equations is to ensure that the number of atoms is the same on both sides.
Step-by-step explanation:
The first rule of thumb for balancing chemical equations is to ensure that the number of atoms is the same on both sides. This means that the equation is balanced and has the same number and type of atoms on both sides of the arrow. The coefficients placed in front of the formulas are used to achieve this balance.