Hmmmmm ... high school is a bit out of my ballpark. I'm an elementary teacher so all I can offer is some really general advice.
1) Find and familarize yourself with the district curriculum for Spanish.
2) Get a copy of the faculty handbook to learn about school rules, attendance procedures, grading policies etc.
3) DON'T GOSSIP. There is always an undercurrent of school politics that is going on and as a new intermim teacher you don't want to be seen as "aligning" yourself with one side or another.
4) Be firm - fair - and consistent with the enforcement of your expectations.
Best wishes to you in your new job,