That is a very general comment that you posted. When you are dealing with balancing chemical equations, you may or may not need to take into account whether the reaction even has the possibility of happening. Some teachers throw those kinds of questions in there just to see if you paid attention in Chem 1. Reactions may not have a chance of happening unless maybe temperature or pressure play a part along with the possible introduction of a catalyst. When I use to balance reactions, I would always start with the more complex molecule. Example: in the reaction above, try to balance the sodium nitrate and the sodium oxide first and then the sodium solid and the nitrogen gas. Balancing a chemical reaction also depends on the reaction itself, more directly, what kind of reaction (i.e. ox/redox, substitution, etc.) because you can complicate things by having to take into account oxidation numbers. Most important: start with the most complex molecule and then finish balancing with the simple molecules or elements. Hope this helps.