Superpang, forgive me if you know this but I must share...don't for one moment think that travelling domestically in India is remotely like anything you've ever experienced in Australia!
Years ago, I worked in India and my (Pommie) boss once said to me..."The British brought burocracy to India, and the Indians perfected it!" Never a truer word spoken.
Even if you are travelling with hand luggage only and have checked in online, make sure you get to the airport at least 90 mins before departure; I'd advise longer if you need to check in anything. Invariably there are Heathrow-during-the-Olympics style queues around the block for everything, and things move with all the speed of a slug on weed.
If you have checked in online, the check-in staff need to see some ID and stamp your BP. If you haven't had it stamped, the security officials won't let you through.
If they do let you through, make sure you keep your BP about your person and not in a bag, as it needs to be stamped again when you pass through security. Expect to be parted from your bags for several minutes, because the x-ray machine and the pat-down officials (there is a scanner, it always beeps, and you always get manually scanned) do not work synchronously, so keep a close eye on any valuables where possible.
Make sure that you have cabin bag tags on everything - they need to be stamped when they've been x-rayed. There are lots of people with lots of stamps...
Finally, if you have a travel companion of the opposite sex, don't expect to be able to chat to him or her in these seemingly-never-ending queues, because boys and girls get their own lines!
Dont get me wrong, I lived in Bombay for a year, loved it and have been back twice since I left, but things just aren't quite the same...
Good luck, and have a great trip... embrace the food, the culture and the people, it is a wonderful country!
Cheers,
D-H.