Well, you take a clone or a seed, put it in a netpot with hydroton and let push its roots down into the bucket. Hydroton has to be kept wet untill roots reach the water level. Often water bubbles are enough to keep the medium moist enough (you can add extra water pump, but then be careful not to drown your plants, specially if you are using rokcwool cube). Bucket should at first be filled with pure water at first, and later, when embryonal leaves start dying, nutrients should be added. Nutrient solution should be changed optimaly every 7 days. At first, you'll be throwing up a lot of it, later on when plants get bigger, they will drink up to 3/4 of the water available in 20 L bucket. You need a lot of air (1 litre of air per minute per gallon minimum), your setup has to be kept light proof (if any light enters into your bucket, you'll end up with large problems), and the water should be kept at about 18 to 20 C. Never EVER add anything organic to your res, just pure inorganic nutes (forget about aditives).
Also, all the way from the begining go with some EWC tea as explained in heisenbergs sticky topic.