Initially, Noah has no clue of the actual, supernatural elements of Beacon Hills going on within his town which hampers his ability to do his job in spite of Stiles and Scott encountering and fighting against them on a nightly basis.
Finally, in Season 3, he is let in on the supernatural business, he's less than thrilled, but uses his newfound knowledge and perspective to solve cases old and new more effectively, and enlisting the help of Scott's Pack in solving crimes concerning those elements.
A werecoyote, Malia involuntarily changed under the full moon as a child and caused a car accident which killed her mother and sister. Scott accidentally bit him trying to save his life and he consequently became Scott's first Beta.
In Season 3, she embraces her family legacy as leader of her family. The original Beta werewolf in town, Derek is a swirling mass of mistrust, misplaced aggression and anti-social behavior.
He seeks out Scott after he is bitten and offers his help, but his standoffishness and secrecy often let Scott to question his motives.
Originally a somewhat nerdy, asthmatic outsider with little friends, his life changes dramatically after a fateful meeting in the woods leads to his transformation into a werewolf.
His new powers grant him athletic prowess and more popularity, but they also open up a world full of danger and supernatural enemies.