A net ionic equation only shows the substances that are involved in the chemical reaction. We have to expand the compounds in aqueous states, turn them into ions, and delete the duplicated ions from both sides (if possible).
So first step, write the full ionic equation. Just expand all the aqueous compounds. Other compounds/elements not in aq can be left alone and be copied directly. Make sure to write the state symbol too for each ion.
2KOH(aq) + H2SO4(aq) → 2H2O(l) + K2SO4(aq)
will be
2K+(aq) + 2OH-(aq) + 2H+(aq) + SO4 2-(aq) → 2H2O(l) + 2K+(aq) + SO4 2-(aq)
Now, just delete the duplicated ions. We see that 2K+(aq) and SO4 2-(aq) appeared in both sides of the equation, so just delete them to get the final answer!
Therefore, the net ionic equation is:
2OH-(aq) + 2H+(aq) → 2H2O(l)
