There are four ways to get Valor:
100: First heroic Warlords dungeon of the day ( Daily Heroic Random (1st) (Draenor)). Awards up to 700 per week if done daily.
300: Completing each Mythic dungeon for the first time each week. Awards up to 2400 per week if all eight are completed.
500: Completing the weekly bonus quest (pets excluded).
150: Completing a wing of Hellfire CItadel LFR ( Raid Finder (1st)) for the first time a week, there are 5 wings total. 750 if all five wings are completed.
75: Completing a wing of Highmaul or Foundry LFR ( Raid Finder (1st)) for the first time a week. There are 3 Highmaul wings and 4 Blackrock Foundry wings. 525 if all seven wings are completed.
The maximum you could acquire per week is 700 from Heroic Dungeons + 2400 from Mythic Dungeons + 500 from event + 750 from Hellfire LFR + 525 from Highmaul/Foundry LFR = 4875.
What about leveling up and then telling GMs, that you leveled by mistake and want to delevel? I red somewhere, that they changed their policy about deleveling and it is now possible. But question is, if you will keep your Valor points or they will be removed as part of deleveling.