I'm looking to book an India-US one-way mileage ticket. Not sure how to go about it.

I have lots of Delta miles, AA, AS, BA, and some US and CO. Delta's website was not very useful. (Also, in the future I'll probably be booking RT flights).

Any suggestions on how to book this? Helpful websites, routing suggestions, partner info?
Alternatively, information about purchasing cheap flights would be helpful.

I thought this information would be out there somewhere, since flights to India are so common; just couldn't find it.