Lupita,
Hi! I run the web site for a well-known author. I basically have been someone's left arm [on edit: or is it right-arm? Whatever!] (personal assistant-type) all my life. Along the way I've learned all about business, negotiation, contracts, etc.
I don't know a lot about the teacher/student relationship from your end of it. I've been a student!
I would guess it remains the same with any incident that pops up - any disrespect or insubordination needs to be addressed on the spot. For me, like with my son at home, I let it be known I have a zero tolerance policy for certain things. I am more flexible on others. When he knows the rules, there are no arguments. I have not had a whine or argument from my son in....I can't remember the last time. But, he IS unusually bright(!) (said with a wink).
It's so much easier to say than to do, Lupita. I know that. To be in your shoes, would be terrifying for me. I know how intimidating some kids can be. Certainty is the key. And having a plan. If the kid does this (swear, be 3 min. or more late for class, etc.) then X is the consequence (detention, a trip to the principal's office where paperwork will be put in the file, etc.). Try and make the consequence fit the crime as fairly as possible. If you let one thing slide, everyone will notice and then there will not be that respect that's needed to motivate them to obey you.
My grandmother was a brilliant teacher. She always had her kids rapt with attention. I don't know how she did it, but she had a presence. She always asked thoughtful questions.
I hope this helps a tiny bit.
Hugs,
Dandylife