hi ableze, i understand your concern. it's normal to ask about the salary but find it hard to mention it. it's important to wait for the right timing...  normally the interviewer will talk about it first. but if he/ she doesn't, and you find the interview is about to end, it's the time to ask. Take the opportunity when he/ she says: Do you have any other questions? ... say yes, and that you would like to know about the basic (pay) of the position. I figure that's the polite way to ask

And as for thank you letter and what not... i think it's not necessary too. but if you would like the interviewer to remember you, send a thank-you email. normally when they come in, they'll pass/ present you with their business card and in there states their email. So just send them a formal thank you email for seeing you and that you'd be waiting for their call on the next round of interview