Something that I've found by observation: If you notice any sensation of dryness in your mouth, then you are not properly hydrated. For me, this observation direclty correlates to other factors of recovery, like sleep. If you are curious, try the following experiment: Keep your water/fluid intake down to an absolute minimum (or even suspend intake for 16 hours) and see how you sleep. If I do this for even one day my sleep goes to hell along with recovery, of course. Once my fluid intake is upped again and my system reaches a properly hydrated state, sleep once again becomes deep and restful. Drink LOTS of water.
"Lack of sleep makes cowards of us all."