There is no hard and fast rule for how much water to drink. The volume varies and depends on body size. 6-8 glasses (8 oz) seems to be a recommended amount for most people.
However, there are some better times to be drinking water rather than haphazardly:
After waking up 1 Glass of water helps activate internal organs…
30 minutes before meal 1 Glass of water helps digestion
Before showering 1 Glass of water helps lower blood pressure
Before sleeping 1 Glass of water helps avoid stroke or heart attack
Source: Reg Rea, In House contributor