water when the first few inches of soil is dry. start feeding after the first 2 weeks of plant growth with half strength nutes. build your way up as the plant gets bigger it will use more nutes. balance the nutes right for each stage of growth only feed every other watering. make sure your ph is 6.5 little more or less. test your soil often. as to what nutes to use, its up to you. seedlings like npk of 20-20-20 half strength at first then after about a month when it starts to take off, you can drop the p to 10 and raise the n to 25 with k at 20 with micro nutes.(25-10-20) when flowering drop the n to 10 and raise the p to 25 with k at 20 with micro nutes.(10-25-20) -USE WHAT WORKS FOR YOUR PLANTS, THEY WITH TELL YOU IF THEY LIKE IT OR NOT-
Tdeg has some good info there x2. Seedlings start needing weak nutrients when the three-bladed leaves begin growing in. Usually at this point the plants are just transplanted into larger containers of nutritious soil. Same thing with clones once they're rooted. The NPK ratio on containers of fertilizer list the percentages of each macronutrient that make up the unmixed fertilizer inside the container. Once properly mixed, most fertilizer solutions end up under .1% of any nutrient.