Language in India: India is home to dozens of different languages and dialects. The most commonly spoken include Hindi, Bengali, and Marathi. If that seems a bit overwhelming, don't fear, English is widely spoken.
Currency in India: India uses the Indian Rupee (INR). At time of writing, £1 is 108 Rupees. Indian Rupees are closed currency, which means they're not available outside of India. Therefore I recommend bringing cash to change, or a travel-friendly debit card.
UPI in India: UPI is India's main method of payment, essentially allowing you to scan QR codes for vendors to pay for things. Everyone from big hotels and restaurant brands down to tuk tuk drivers have a QR, making fishing for change largely a thing of the past. It's a bit of a faff to set up, but so worth it. We used Mony, however I would exercise caution with how much you load your account with, as it took absolutely ages and lots of following up to get the excess amount refunded when we left. Altneratively, Wise recommends Cheq UPI and ICICI Bank iMobile Pay - if you try either of these, do let me know how you get on!
When to Visit India: As India is such a vast country, the best time to visit weather-wise varies drastically depending on where you're planning to go. For most parts of India, Winter (December-March) is peak season, when the temperatures are cooler and more manageable. However it may be cold in the more mountainous Northern regions at this time. Summer (June - September) sees Monsoon season descend on the middle and south, whereas the northern regions will be more temperate.
Getting Around India: India has every sort of transport readily available, and you'll most likely get around with a mix of all of them. The train system is comprehensive and your main port of call for travelling between cities. You have two main booking options. There's 12GoAsia, which hosts all the most popular routes, however charges a hefty markup. Or, if you have the patience, you can set up an account with Indian Railways (this blog post outlines how to register). It's a faff, and the website isn't the easiest to figure out, but you'll have more route options, and be paying far less.
For journeys not connected by train, India's domestic flight network is available, with domestic carriers including Spice Jet and IndiGo. They're not always the most reliable (cancellations and delays aren't unheard of), so give yourself a buffer when travelling by plane.
Within cities, use apps like Uber and Ola to get around. You can book Tuk Tuks and cabs, with set destinations and fixed pricing making getting around hassle free.
Safety in India:Â India does not have a great reputation for safety, and this is not completely unfounded. But like any destination, if you exercise caution and keep your wits about you, you shouldn't run into any problems. For example, keep an eye out for scams. People trying to take you to a friend or family member's shop, for instance - they're likely getting a kick back, or will try and charge you exorbitant prices. At railway stations, people posing as staff may try to tell you you have the wrong type of ticket, and take you to a fake ticket office to buy a new one. Oh, and read hotel and restaurant reviews thoroughly, looking out for red flags - they're often fake.
India as a Solo Traveller: Though I'm sure there are many who have travelled India solo with no problems, it wouldn't be my top choice as a solo travel destination. You're liable to receive a lot of attention as a foreigner, which I imagine could make you feel quite vulnerable when travelling solo, particularly if you're female. If you're a solo female traveller, consider joining a group trip such as those run by Intrepid.
What to pack for India: It's likely going to be hot, so loose fitting cotton and linen clothes will serve you well. It's common for women in India to cover shoulders / décolletage and legs, so I'd recommend choosing clothes that do so, as you may attract unwanted attention otherwise. Comfortable, sturdy sandals for uneven, dirty roads are a must. I say this with every destination, but a shawl for temples, mosques etc will always come in handy!
If you're interested in Indianwear, the best selection will always be found in the country. However some of my favourite brands that ship internationally are Laksharaa and Kalki. For shawls and modest clothing, I find the best selection comes, funnily enough, from modest wear brands - some of my go-tos are Aaliya, Aab, and Podur. The latter does some really gorgeous modest dresses!