Is there a method for finding the net-ionic equation?

I truly don't understand the method for finding the net-ionic equation for a reaction. It is not clear to me how you should decide what the products are, especially when there are multiple possibilities. 


**Example:**



> 
> Excess potassium cyanide solution is added to aluminum bromide solution. 
> 
> 
> 


The first thing that came to mind for the molecular equation is:


$\ce{3KCN\+AlBr3 \to 3KBr\+Al(CN)3}$


But apparently the correct molecular equation is:


$\ce{6KCN\+AlBr3 \to 3KBr\+Al(CN)6}$


I see no good reason why the one I thought of is incorrect. And to get the net ionic equation, the spectator ions are $\ce{K+}$ and $\ce{Br-}$. But why should I assume the solution is aqueous?


**Another example:**



> 
> Chlorine gas is bubbled through dilute sodium hydroxide. 
> 
> 
> 


Well its easy enough to get the reactants:


$\ce{Cl2\+NaOH \to ?}$


What first comes to mind is $\ce{Cl2\+2NaOH \to 2NaCl\+Cl2O\+H2}$


But the correct molecular equation is $\ce{Cl2\+2NaOH \to 2NaOCl\+NaCl\+H2O}$


What should be the thought process for arriving at the correct answer here. I am truly lost.


**Another example**:



> 
> Lithium oxide reacts with sulfur dioxide. 
> 
> 
> 


I recognize this as a synthesis reaction. However how can I predict if the product is lithium sulfite or lithium sulfate?





> 
> But apparently the correct molecular equation is $\ce{6KCN\+AlBr3 \to 3KBr\+Al(CN)6}$
> 
> 
> 


That's not correct, what happenend to the other 3 potassium atoms?


It could form $\ce{Al2(CN)6}$ but you can't exclude $\ce{Al(CN)3}$ without further information beyond balancing of equations.


There are two main steps to balancing equation:


1. Balancing of each type of atom
2. Balancing number of electrons


If you've done both of those correctly, you've done all you can with balancing alone. 



> 
> $\ce{Cl2\+2NaOH \to 2NaCl\+Cl2O\+H2}$
> 
> 
> 


Above is clearly wrong because number of oxygen atoms doesn't balance



> 
> $\ce{Cl2\+2NaOH \to 2NaOCl\+NaCl\+H2O}$
> 
> 
> 


Above is clearly wrong because number of oxygen atoms doesn't balance


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