Well, season one sucked, so its no wonder you stopped.
A Head of Household (HoH) is determined by winning a competition. the HoH then nominates two people to be eliminated by the rest of the houseguests. The two nominated people the HoH and one person that each player picks to play the Veto competiton, where you can save one person from the nomination block, and then on Thursday, a person is voted off by the rest of the houseguests!
Rob