I water until it comes out of the bottom of the plant (make sure you get full coverage around the pot the are in). As long as you let them dry out between watering it is hard to give them to much at one time.
I am not an expert, yet, but I water my 5 gallon buckets with a gallon jug. I give each bucket a 1/2 gallon then wait a few minutes before I add a quart more, and so on until it begins to just run out the bottom. I call it quits as soon as I see the water escaping into the tray at the bottom of each bucket.