ive never really used water when mixing protein if you use milk i would use 1% or skim milk for the lower fat content.
but the main thing is the actual protein that your using.
things i look at when purchasing
1. Grass feed cows (over grain feed)
2. protein per serving
products i would recommend (and use)
1.
100% Whey Protein For before or right after workout
2.
100% Casein Protein A slower digestive protein many use when going to sleep so your body has some protein intake during those long hours of sleep
a good site for some research on everything not just protein
http://www.bodybuilding.com/store/top50.htm