For a bottle like this, I chopped up about an inch of ginger root, three small lemons without seeds or skin (or Meyer lemons! They're at TJ's now and are a cross between lemons and clementines.), four cups of water and threw it all in the blender.
If you don't have a blender, mincing the ingredients works just as well. If you REALLY want to get a refreshing "Aaaah..." with every sip, chop up a few mint leaves as well. Sugar is totally optional and should be used sparingly if at all.
Happy Spring, everyone!