To qualify for Auror training, a witch or wizard had to first have attained at least five N.E.W.T.s of no less than 'Exceeds Expectations'. Minerva McGonagall recommended that Defence Against the Dark Arts, Transfiguration, Charms, and Potions would be useful N.E.W.T. level classes for those wishing to pursue a career as an Auror.

Whereas the Ministry set a series of character and aptitude tests to further test the worth of potential applicants, it was also possible for someone to be offered a job in the Auror Office if one of its high-ranking and influential members deems an individual to have displayed sufficient ability to be qualified, although they still have to undergo the required training programme in order to become a fully-fledged Auror. The Ministry also runs a background check into the records of new applicants; Dolores Umbridge once implied that wizards with a criminal record cannot become an Auror.

It will be usful if you know how to read Ancient Runes, or at least are learning it. First years? I am sure that you can take the Runes still. However, you don't have to.