This will obviously depend on which trek you are doing, at what altitude and during which season. Nepal is at the same latitude as Florida and Kuwait so the sun can be very hot. However the temperature drops by around 2?C with every 300m of altitude and in the winter it can be cold even at lower altitudes. As with European hiking the best approach is to adopt a layering system so layers of clothing can be added or removed as the temperature changes. Nepali culture is conservative so the clothes you wear should be neither tight nor short especially for women. Long clothes also help protect against sunburn and insect bites.


Most people will pack too much and there seems to be plenty of advice on how to keep it light such as getting together everything you think you will need and then discarding at least a third of it. It has been suggested that the optimum number of socks you need to carry is three - each day you wash one sock so you never wear any sock for more than two days! However this doesn't take into account what happens when you get both feet wet or having a particularly acute sense of smell for that matter!
Packs: At the end of the day you will probably have 1 porter between two people and each porter will carry a maximum of 25 kg. It is advisable to pack things in either a lockable duffel bag (available in Kathmandu) or a backpack. Pack clothes in plastic bags to keep them dry. You should carry a day pack with you when trekking containing an extra layer, suncream, water, snacks and valuables etc.


Clothes: A general rule is to take two of everything. A couple of pairs of cotton trousers and a pair of long johns for any colder spells will usually be fine. However in the winter at altitude it can be severely cold and a thick pair of trousers (and possibly windproof over trousers) is recommended. For lower altitude treks in the warmer months you may want to take a pair of shorts and one pair of long cotton trousers.


For the top half of your body you'll probably be happy enough with a couple of T-shirts and a long sleeved shirt(with a collar to protect against sunburn)for most of the time. You should also take a fleece jacket or pullover for evenings. During the colder months you may like to consider taking a down jacket although extra layers and two fleeces worn one over the other may suffice as a cheaper option. If it's likely to be cold thermal underwear is strongly recommended. Some kind of waterproof jacket is recommended although this doesn't have to be an expensive hi-tech affair!

3 or 4 changes of underpants or knickers is fine and a couple of bras for the lasses! Wearing a pair of thin socks under thick socks is supposed to help prevent blisters (which can ruin a trekking holiday) and you don't have to wash the thick socks quite so often. If you have enough room in your boots to do this then take 2 pairs of thick socks and 3 of thin. If you only wear thick socks then take 3 pairs. Wool and cotton socks are best as synthetic socks tend to rub. If you want to wear ordinary socks as liners you should make sure there are no thick seams on them which could cause blisters.


Other items of clothing to take are: a wide brimmed sun hat to protect you from the sun during the day and a warm woolly hat if it is likely to get cold (40% of body heat is lost through your head)! A pair of sunglasses is essential and if you're likely to be on snow for any amount of time (days spent crossing high passes etc.) then ski sunglasses with side protection are recommended. A pair of gloves or mittens is essential.


Other items which are very useful are: a sarong - this is particularly useful for women if there is no suitable shelter for toilet stops, is useful for bathing in public and can double up for a variety of uses such as a sheet to cover yourself with during the hotter nights, a shawl for extra warmth on colder nights, a towel etc. Taking a silk scarf is also a good idea as it is very useful to wear around your neck to protect the back of your neck from becoming sunburnt (a common occurrence). During the spring when there can be a lot of airborne dust it can be worn as a face mask over the nose and mouth. It can also be used as a hairband on windy days, an ear warmer, a bandana in case you lose your hat, and as a flannel for washing purposes.


Footwear:

A good pair of walking boots which are well broken in before the start of the trek is absolutely essential. There is a wide range of boots available on the market and which one you choose is really down to personal preference. They should however have good ankle support to prevent sprained ankles and some stiffness in the sole helps to support your foot. If you opt for fabric boots they should be waterproof and able to keep your feet warm if you are likely to encounter snow (for example when crossing the Thorung La).


You may want to take a pair of trainers (with good grip) as a back up to your boots though this isn't really necessary. A pair of lightweight sandals such as Tevas or just flip flops are a good idea for when you aren't trekking. If you want to be able to wear these with socks then avoid the thong type of sandal which have a part between the toes. If it's likely to be cold you may like to invest in a pair of cheap down booties which are available in Kathmandu for around $6 and are good to wear in bed at night if you're prone to cold feet.


Sleeping Bag:

Whether you are staying in tea houses or camping you will need your own sleeping bag. Down is lighter and packs smaller than synthetic bags although there are some good lightweight synthetic bags on the market now. How thick a bag you will need will depend on how high you are and the season you trek in. However unless you're on a mountaineering expedition you won't need an expedition bag so the thickest bag you're likely to need for trekking is a four season bag but in the pre-monsoon Terai you'll be too hot in just a mossie net!!


Toiletries: There is a good range of western toiletries available in Kathmandu's Thamel area. Only take toiletries which are essential and try to use small travel bottles of things like shampoo. Soap is better than shower gel as it can be used to wash your clothes as well. Sunscreen and lip balm are absolutely essential as UV is stronger at altitude and you're a long way south! If you're packing toilet paper take a cigarette lighter so you can burn it after trail side stops. You will need to take a medical kit with you and a syringe kit is recommended.


Towels: As towels are big and bulky there are a few alternative choices. Lightweight travel towels are available from most outdoor equipment shops. These come in various sizes and although lack the luxury of a big fluffy towel work perfectly well and dry very quickly. There are two types available, the extra soft option is the nicest! Other options are to use a flannel, a tea towel or a sarong.


Other miscellaneous items include: a pair of telescopic trekking poles to save your knees when trekking is highly recommended. They're also good to have for added stability especially if you lack confidence on steep descents. A torch with spare batteries and bulb, camera with spare battery and films, a water bottle of at least one litre capacity, water purification equipment or tablets, sewing kit, a short length of cord (for drying clothes), penknife (Swiss army variety is best), guidebooks and maps, reading matter (there are a number of good book shops in Thamel which sell first and second hand English language books and will buy your books off you) and a diary - keeping a diary gives you something to do in the evening and is a great memento of your trip. Finally don't forget your passport, insurance documents, currency and flight tickets!