Sort of depends on what kind of soil you're using. If it already contains time-released fert(like Miracle Grow), then every third watering would probably be best. If it's a quality organic mix, then every other watering is fine.
depends how strong you did it.
I feed every watering but at 1/4 strength, I water first too then add the nutes after I've seen a good runoff of water. I'm using soluble 20-20-20, one level teaspoon to a gallon of water. One cup of solution to a gallon soil.