As dumb as it sounds, that kinda depends on the plant. This is my second grow, and I watered my first grow too much, so the leaves were wilted. Now I water my plants every six days it seems.
Here's the general rule of thumb. When you can poke your finger into the dirt 2 to 3 inches and it feels dry, then water. Water enough so that the water drips out the bottom of the bucket. Then wait until it gets dry 2 to 3 inches in the soil again. You'll figure out from your setup what your plants like best. Hope that helps!