The first step in writing a net ionic equation is to determine the reaction that is taking place and the states of matter in which each ion can be found. Once this is determined, include only the reactants and products that change state of matter and electrical charge.
It can be helpful to write the overall reaction as two half reactions to better visual the ionic changes. Net ionic equations include only ions that participate in the overall reaction, so ions that are aqueous on both sides of the equation are omitted. Knowing the solubility rules can help predict the outcomes of a net ionic equation.