Forget the words superior and inferior, they are a poor fit it my experience.
Social elevation. Either you shall raise your friend or you shall lower yourself.
You may do both, but do not do both in the same sentence.
It is okay if you make mistakes and mix and match, but if a native speaker did it it would seem rude by "laying on the gravy of politeness"
So, depending on how much you have learned, always try to use keigo for the teacher's actions.
The sensei irrassharu's (arrives, leaves, and any te-iru)...
The sensei ossharu's (speaks, elocutes) and not just "says"
"Oshatta toori" or "As you have said" is a great phrase to use in pretty much any situation where there is social elevation.
Humbling language... hmmm. ~~to moushimasu and the like? Yeah, it's good, but in my experience people get a bigger kick out of you being able to raise /their/ level than diminish your own. If you are in front of many people or in a crowd of sensei(s) then you will want to use this because it's important to be humbled-by-your-peers.
In groups of friends whom you are hanging out with, use whatever other people are using, and it is definitely OK to ask what level of politeness.
People might ask your age and address you accordingly, like if you're older they might start adding desu to everything. I think the best course of action is to say "you need not use polite language regarding me" or "watashi ni taishite teinei go wo tsukawanakute mo ii desu yo." Just some personal preference at play. Have fun and immerse yourself as much as possible.
Always be listening to Japanese and always be practicing sentences. In the shower, on the walk to the train. Tiny moments of practice add up! When you can master the pitch intonation (by repetitive listening to sound files or the what like) then people will truly be impressed! (bit of a rant at the end but I wanted to add what might be useful for ya!)