check out Technflora's Recipe for Success. It is a complete package of nutrients that will take you from starting into veg and right on through to flowering. Its a good place to start. It also will have complete instructions on how to use the products. But make sure you are letting the soil dry out completely before watering. Its soooo important that they have wet/dry cycles so they can have the best uptake of nutrients.Technoflora recommends a water, water, feed cycle. But with certain high energy plants under HID it might be better to, as Dalo818 said, feed every other watering with half strength nutrients. But if you are using lower powered light less nutrients will be better for the plants.