This is the most exhausting travel I've done. Indians are... I'll be short and clear : I don't like them. Specially because they make me acting like an asshole at least once a day. The funny thing is, I don't like them but I still like the country. What I've seen in India is amazing. I usually know what to write about my travels, but for India, I still don't know after 2 months. Maybe because I might spend 2 days writing about it (colours, landscapes, palaces, forts, Taj Mahal, ...) or either not saying anything but 'get fucked !'. As many travellers who had experienced the country, you must have left it to sort out the good of it.
If you guys want to come to India then I would recommand to come for a short period with plenty of money. Over a month stay ? Keep breathing and take an extra 2 weeks off to relax.
India is incredible. They spent millions making ads all over the world (have a look on youtube they are quite nice) saying 'come here it is nice' and if you need a bus going to somewhere a little bit unusual, no one is able to tell you how to do. And if you do get a bus or train, then be ready for a very long trip. In two months, we spent over a week time in the transport.
Here are my advises for India : No need to go to Delhi. Nothing to see there. Or you can see better somewhere else. Varanasi is an amazing place, Khajuraho is another one. Jodhpur, Udaipur, Jaisalmer (and is open air rubbish bin Thar Desert), Pushkar are also to be seen. And if your up for a 30 hours of dusty road trip with filfthy Indians sleeping on your shoulder, do not miss Ajanta and Ellora Caves. From there, you'll go to Bombay (so british ! My favourite big city in India) before to go to Goa having a grilled fish on the beach (please do not have those little sharks... It might be good, but they are far too small to be in your plate !). If you feel brave enough, you can have a swim and get tanned on the sand. For myself, I was there during Christmas and too many tourists were spitting on the sand. And I can't avoid the fact that every year, the rain bring the rubbish into the sea...
I'm really happy about what I've been doing here and I'm even happier because I'll be soon far away from the mess and those auto-rickshaws fuckers or these awfully non-heartbreaking robotized children beggars (all over India, all the kids will always come to you doing the same hand to mouth gesture as there is a king of school where they learn it. Most of them ask you just because you're white - I guess this is fair enough - but they seem to be happy and healthy).

Read Shantaram by Gregory David Roberts, Holy Cow by Sarah Macdonald and Are you Experienced ? by William Sutcliffe if you want to learn more about the idian experience.