[macman104]

My text says keeping the reaction cold and dilute favors diol, and concentrated and hot favors cleaved products (ketone/acid - depending).

That is the way I was taught and is the way it was presented in my book as well.  Cold,dil = diol; hot and concentrated = ketone/acids.

As far as the reaction I mentioned earlier, it is required that there is at least one hydrogen in the benzylic position, as it is susceptible to attack by an oxidizing agent. You can check here and scroll down a little bit.  It may very well be something only discussed in upper-level courses...