Ladies should wear sports bras - especially if sitting on the back seat of the bus! Despite following all the safeguards closely, almost everyone developed one form of Delhi Belly or another. Locally bought medication was very effective and cheap as chips! I believe the local "dioralite" equivalent is vile so bring your own. We had excellent advice from Pravar (tour leader) to drink loads of water right from the start and so drink it whether you feel like it or not. You will be surprise how little you pee!
My friend and I travelled from Manchester - arrival at aiport 3 hours before flight, 8 hour flight to Dubai, then a 3 hour wait at Dubai for the connection to Delhi, then another 3-4 hours. The long drive from Delhi aiport to our first night-stop (Jaipur) on top of everything was a killer. I would certainly recommend getting to Delhi the day before and getting a decent night's sleep ahead of the bone-shaker bus ride to Jaipur!
We chose the evening flight to return to the UK so it meant we had a full day in Delhi - ideal for hiring a taxi from the hotel (1700 rupees for 8 hours or 80km) for sightseeing. There were 6 of us sharing and we paid 300 rupees each (just over £4!)