There's nothing especially different in filing from the US. I have found it useful even when applying to public authorities like SEBI and RBI, to send my RTI request to the PIO of the Indian consulate, NY (Dr Neena Malhotra, details on the web), and ask her -- invoking s6(3) -- to forward it to the appropriate PIO at SEBI or RBI. To pay the application fees I have either had friends in India buy a postal order, or have used online purchase of demand drafts. (In part this was because at that time she had no clue to what to do regarding collection of fees.)
I know others who have identified the correct PIO in India and directly sent their RTI requests by email or snail-mail. While there can be problems persuading a public authority to take cognisance of an RTI request, the problems are not unique to not being resident in India.