Hund's Rule: When the all electrons will fill in each orbital first with the same spin and are parallel until there is no more orbital to fill in. In another words, the electrons do not want to be "with each other" or in the same orbital or box if you are talking of orbital diagram. The p orbital has 3 boxes right? If you were to fill 2 electrons in the p orbital, you would put one eletron is one box and then skip to the other box to put in the second one.
Aufbeau Principle: The electrons entered the atom in the lowest energy level. That means it cannot enter from, say energy level 4 and then go to energy level 2. Got it?