x-posting from Nukkad and continuing here
In addition to all of the useful suggestions already provided--
Some thoughts and I don't mean to be gratuitous:
If you are planning on doing some trekking with a pack load on your shoulders, you would do well to be kind to yourself. No matter how much of a Rambo one thinks of oneself, after the first 2 kms, every gram counts and makes its presence felt, painfully and persistently on the back and shoulders. Double this if going uphill.
You can either be a pack mule or you can enjoy the trip.
There is good quality gear at a price and there is good quality light gear at a (sometimes much) higher price. It pays to get the lightest gear money can buy. You, your back and sanity will be thankful for it and not only will you enjoy your trek but also have some allowance for the inevitable souvenirs that will find their way into your pack. Plus you do not have to worry about luggage weight at airline check in.
Unfortunately, unless you get creative (and this is possible) light gear costs much higher. There is simply no way around it.
The biggest contributors to weight are:
1. The backpack itself - Get the lightest one that money can buy. Aim for a range of 800 gms to 1.5 kgs. Yes, Its possible. While at it a 2 litre water bladder could be useful if water availability is going to be iffy.
For Indian Railway cloak rooms, ensure all compartments of the pack are lockable.
2. The tent - 3 or 4 season? How much wind protection? There are plenty of ultra light choices depending on the answer to these questions. For a 4 season around 1.5 -2kg is a good target.
3. Food - are you going to be catered? If cooking your own what type of meals do you wish to eat.Desi/Videsi/anything goes?.
After cooking dal-chawal and kichhidi type meals from first principles for a long time, I have now switched to dehydrated meals to which I simply add hot water. When away from civilisation, I enjoy 3 hot meals every day consisting of stuff like, poha, upma, puliyogare, dal fry, rice, bisi-bele-bhath, kicchdi, rajma, chole, bhindi, palak paneer - the works.
There is nothing as satisfying and good for the morale at the end of the day as a piping hot Indian meal.
Instant coffee and tea packs are also readily available in desh.
And how are you going to cook this meal? Propane canisters are very tough to get in India. I use a alcohol fuelled Trangia stove. This amazing Swiss stove is an off shoot of a Swiss army stove design and I have cooked meals in 50 kmph winds with heavy downpours. It is wind and water proof and has no mechanical parts.
Alcohol (methylated spirit) is easily available in India in Pharmacies. A a last resort find out the suppliers to local school chemistry labs - they always have it.
A further benefit of alcohol is that it can be used to treat wounds, cuts and bruises. If its spills in your backpack it simply disappears without a trace. Since it looks like water and is very corrosive if ingested, I always keep in a bright and differently coloured bottle.
A dis-advantage is that you need more of this fuel per unit of water as your altitude increases. But since we are only heating water to re-hydrate food its really not much of an issue.
Discard the box cover of the food and lable (very important - as after you get rid of the box, the foil packs all look the same!) and keep the foil packs with the dehydrated goodness.
4. Clothes - layering, layering, layering is the key. Plan in such a way that you should end up wearing pretty much all your layers in the cold and have nothing left to carry in the back. In India, antimicrobial clothes are a god send. Delays smelling like a gutter. A good fleece, wind & water protection and a beanie are essential.
5. A sleeping mat. Thermarest make great light mats.
6. A foldable hat with a chin band so it does not take off in the wind, Rs 2 pouches of Ariel detergent (carry a sink plug and wash your clothes in the hotels sink) & a thin nylon rope to hang your laundry.
7. Anti mosquito spray, good knight repellent for the days when you will sleep with power. Often, clean water to wash hands is not available - a hand sanitiser fixes this problem. An insulated mug will help keep precious tea and coffee warm for longer.
8. Duct tape is like a mother. It fixes all problems (mends tears & breaks). Has saved me numerous times.
9. Oops, missed the sleeping bag. Again get the lightest money can buy for the rating you want. Hooded sleeping bags are really a waste because you will have a beanie.
In the lat 2 years, the maximum my pack has ever weighed is around 16 kgs for my winder expedition to Doda and surrounds. If you are going up the Himalaya's, it could be more. Once I descend, the pack weighs less than 12 kgs with tripod and umbrella and often less than this. For months, I got it down to only 7 kgs. I live out of this pack and I care for my back.
How do I know my pack weight?I have a handheld portable weighing scale that weighs upto 35 kgs
For the day pack I ditched the bulky SLR and carry a prosumer compact that shoots RAW. In the mountains, I ditch the full size tripod and shoot at slow speeds using snipers technique. Plus now days IS is quite good.If I must have greater than 1/15 second exposures, I carry a mini tripod that fits in my palm. What a relief!
I have been backpacking through India for almost 2 years now (and still going). Its been a fantastic experience living out of a backpack and a daypack. From Kerala and Rameshwaram in the south to Bhadawah, Khistwad & Naska in Doda during winter in the North.
This trip I have avoided the well trodden path.
Back where I live abroad in them yonder hills, I have been backpacking for more than 14 years almost every weekend (winters excluded).This is what keeps me sane after my BlackBerry driven week day corporate life. And much of this is off-trail with maps, compass and dollops of misplaced courage:-). And the occasional car camping too with hot showers.
I organised a light tent and Trangia stove for a IA Col. friend and he is having a great time trekking in the Nilgiri Hills with his son. Loves the Trangia.
Have a great trip!