If anyone has both the patience and the knowledge, I would greatly appreciate their assistance - and I'm afraid I do need romanized answers.
Faking it well. It's really a special kind of linguistics all on its own.
All of these things are as spoken by a modern 15-year-old girl raised in Uttar Pradesh, who speaks Bhojpuri,* Hindi**, and English.
1. In Bhojpuri or Hindi, how would she address someone as "Brother" (if it's declined, then, in the vocative)?
2. What word or phrase would she be most likely to use to say "my foster-mother," talking *about* the foster-mother, not to her?
3. Does "Accha!" work if one is seriously startled/taken by surprise, or is it more mild than that? If it doesn't work, what would the reflexive response to a significant surprise be? (Swearing is definitely an option, but do tell me if something is particularly rude.)
4. She has a mentor/teacher figure (adult woman) toward whom she is quite respectful but not very formal, if that distinction can be made. What word would be most reasonable for her to use for this person? How would she say, "my teacher" when talking about her to others? Could she (that is, would she, realistically) turn the word into a title and call the woman by this to her face? If so, what would be the form of the word?
5. What would be a typical mumbled apology, not a "I have wronged you" apology so much as an "I stepped on your foot in a crowded line" or an "I didn't hear you, and am about to ask you to repeat yourself for the third time in this conversation" apology?
6. Are there standard forms of address for strangers, the way I might say, "miss," "ma'am", or "sir" if I wanted to get the attention of someone I didn't know?
7. What mistakes in English would be most typical? I'm thinking specifically of common syntactical errors, but pronunciation, sentence melody, even vocabulary are all fair game if they're what would, realistically, be the most likely to go wrong, especially when she's flustered.
8. What words, phrases, or constructions in Hindi or Bhojpuri are so ubiquitous or so useful that she would be likely to retain them even when speaking English, unless she were strongly motivated to remember not to?
9. If someone (not a child) from one part of India encounters someone else who is clearly from India but probably not the same region, would they start out with Hindi in an expectation that this would be most likely to be understood?
10. What didn't I ask that I should have? What other small touches would help make a person seem more authentically from India?
Also, I'm generally leery of about.com, but this piece of it seems better put together than most. If anyone is at all familiar with http://goindia.about.com/, could you tell me how much credence to put in anything it says, about language or otherwise?
* Yes, I understand that Bhojpuri is close to Hindi, but from what I've read, it's distinct enough to be at least considered a separate dialect, and is possibly about to be (or maybe already has been?) named a separate language, so it seemed worth including them separately.
** As far as I can tell, the language is called "Hindi" or "Hindustani" depending solely on the written script used - Hindi uses (I think) the devanagari script, while Hindustani could be the same sentence, written in the Urdu script. Hindustani also appears to be a more prevalent term for the ethnicity. I've used 'Hindi' in this post based on this understanding, and apologize if I've screwed it up.