i do one example for you, on the complexing of copper(ii) ions with ammonia
eg. we add excess ammonia to aq. copper(ii) nitrate solution.
Cu(NO3)2 (aq) + 4NH3 (aq) -> Cu(NH3)42+ (aq) + 2NO3- (aq)
upon observation, you realise that there is nitrate ions on both side of the equation. essentially, the aq nitrate ion remains as nitrate ion, therefore it can be removed from both sides of the equation. hence, the net ionic reaction is:
Cu2+ (aq) + 4NH3 (aq) -> Cu(NH3)42+ (aq)