I remember the questions you're talking about, and they confused me too.
I think you'll be safe just knowing how to fully balance normal reactions and redox reactions (the whole breaking the reaction into two thing, adding H and H2O, e-, etc thing); oh, and of course balance those Hess reactions.
However, I haven't taken the DAT, so perhaps you should sit down and try to fully understand what you saw in Destroyer. Though I imagine if you can do the above balancing, you can balance just about anything.