50 litres of water per discus minimum. Temp 28-30 degrees celcius. Minimum of 4 to spread the aggression but I'd recommend at least 6. Frequent water changes, I'd recommend a minimum of two a week. For beginners its better to get them at at least 8cm in size. The smaller the more water changes, anything from 100% water change daily, and also they are more susceptible to disease etc. Good quality food. Bare bottom tank is easier to raise the smaller ones, older ones are fine in a planted tank.
I'd recommend a first aid kit for fish of harder to get meds as well. As dennisawesome says keep an eye on them, make sure they all get enough food. IME if one is being excessively picked on and decides to go off and sulk and not eat, its very very hard, if not impossible to get them to start again.