Trekking mans to walk in some mountain whether it is for many days or few. It may led you to the base camp of the Himalayas or just some small hills form where you will have spectacular view of the nature and mountains. To walk in the mountain or to enjoy with them you have to be prepared with essential equipments. That is we use to call trekking gears. We can't say which trekking gears are essential to where or in which season. For those details you can consult to your trekking operator or think in general. It will be always a gentle way to trek with the basic trekking gears because you never know what can be most important items to you in trek. Except the basic food and a room or tent to sleep the following things could be useful to trek in proper way.

Kitbag (duffel bag / duffle bag): For all the treks your gear that is carried by the porters or yaks is best packed in a strong kitbag. A simple design without wheels and without foldable handles is best. You can buy in Kathmandu, although they are not as tough as say the North Face Base Camp Duffel. Mountain Hard wear duffels look tough but are not.

Sleeping bag: Down-filled bags are better. Beg, borrow or steal a good one (ie 4-5 season) because high altitude nights will be cool. Good down is fluffy, light and thick. A muff (an extra section around the neck) makes a big difference to the overall warmth of a bag. Reasonable sleeping bags are cheaply available for rent in Kathmandu. Alternatively add a fleece sleeping bag liner to add warmth to a 3-4 season bag.

Sleeping bag liner: Cotton, silk or fleece. Saves washing your sleeping bag and adds warmth available in Kathmandu.

Daypack: This should be comfortable and a good waist band that transfers some of the weight to the hips is most important. It needs to be big enough to take a jacket, fleece, water, camera and odds and ends. Kathmandu now offers a range of cheap fall-part packs to fantastic Mammoth and Black Diamond day packs, my personal favorite are my Osprey packs though (unavailable in Kathmandu).

Boots: For a happy trek you need comfortable feet. Good boots have: good ankle support, plenty of toe room for long descents, a stiff sole to lessen twisting torsion, and are light because with every step you lift your boot up. Look at the inner lining, a material that eats smelly feet bacteria. Gore-Tex boots have an inner liner that helps with warmth but your feet tend to sweat more in the warmer low country. You don't necessarily need Gore-Tex boots. Good lightweight trekking boots or light all leather boots are perfect. Boots must be lightly worn in before trekking and this should include some steep hills to show up trouble spots.

The rougher the trek, the longer the trek, the tougher and newer your boots should be. If you are trekking in heavier boots then it may also be worth taking along some light running shoe-style trainers (eg Salomon XA's), and wear these for the first few days, switching to real boots in the higher country or when it rains.

Socks: In the low country your feet will be warm or even hot while walking so quality cotton mixes sports socks can work well, or light hiking socks. Three to four pairs are enough. Thick trekking socks are better for higher up and cool evenings, three-four pairs. Mostly modern trekking boots fit snugly so wearing two pairs of socks at the same time is impractical.

Camp shoes/sandals/flip-flops:  Luxury for your feet at the end of the day. Sandals or running shoes (tougher cross-trainers also work, see above). Flip-flops or crocs, available for cheap in Kathmandu, are a necessity for showering during the Khumbu and Annapurna treks.

Fleece jacket/vest: Most trekkers consider this essential, but alternatives are a thick thermal top or a light down jacket.

Down jacket/vest: Almost essential for the cool evenings. If you don't already have a jacket, they are readily available or easily rented in Kathmandu for around $1 a day. A down jacket is the best option, although a vest can also be brought along (ie bring a jacket as well).

Wind/rain jacket: Waterproof and breathable. Gore-tex (or similar) jackets are recommended for treks over passes or climbing trips. Plastic ponchos or non-breathable raincoats are not suitable.

Thermal shirts/underwear: Good thermals, both tops and bottoms, are one of the secrets to cold weather trekking comfort. A mid-weight top (zip-T style) is great for high country day wear. Lighter thermal tops are still useful in the low country and an expedition-weight thermal top is a good warm but light system for the real cold.

Nightwear thermals:  Silk-weight is light yet still warm, but for cooler treks mid-weight is perfect. A toasty (but not hot) sleep is essential for a full recovery.

Fleece/sweatpants:  Great for the chilly evenings, thicker is better (except for when the stoves in the teahouses really heat up!).Readily available in Kathmandu.
Prim aloft pants are the expedition camper's best friend though.

Day-wear shirt:  T-shirts are popular but a travel shirt is more versatile. The collar protects the back of your neck and the sleeves can be rolled up or down. Take two so you can swap damp for dry.

Trekking pants: You will live in these. Light material, loose and medium-colored is best. You can survive with only one pair, although two is better, and if heading high, a soft shell pair is really useful.

Wind pants:  If you have soft-shell trekking pants then special wind pants are not needed. If you do bring a pair, it is not necessary to have Gore-tex. Similar, non-waterproof is quite OK.

Underwear:  4 to 7 pairs.

Warm hat/balaclava:  Nice for the evenings, and useful for cold trekking days. Beanies work, so do buffs.

Neck gaiter:  For winter trekking a fleece neck gaiter is really the best for staying warm! A buff is versatile on less cold treks.

Trekking poles:  Definitely useful, especially on steep, rough terrain, but if you are not used to using them you can survive without. One can be useful for easing long descents.

Sunglasses:  Bring good wraparound glasses suitable for snow, its bright up there, but specialized glacier glasses with side pieces are not needed. Contact lens wearers report very few problems except cleaning them in the conditions. Ski goggles are unnecessary.

Mittens/gloves: A good pair of wind-proof gloves is essential. Available in Kathmandu for cheap if you don't have a pair.

Water bottle: Should be one liter or more in capacity, take boiling water and be leak-proof. Nalgene or a similar brand, or European Aluminum bottles, are best, all available in Kathmandu. You need a minimum of 2 water bottles, or at least 1 water bottle IN ADDITION to a Camelback or hydration system.

Pee bottle:  Very useful on cold high country nights! Can buy a cheap one in Kathmandu.

Torch / Flashlight:  LED head torches rule, the Black Diamond ones seem to be better than Petzls now. Available in Kathmandu.

Toiletries and odds & ends:  Essentials for the month only. The smallest tube of toothpaste available in Kathmandu is perfect for a month. Teahouse trekking, there are a surprising number of showers or buckets of hot water available. We provide toilet paper for expeditions; you bring or buy along the way for tea-house treks. Deodorant can spare you grief with your room mate/tent partner... 

Towel:  Bring only a small one trekking, or a camp towel. In Kathmandu the hotel supplies towels.

Sunscreen and lip balm with sunscreen: The sun is strong at altitude, especially after snow. Bring at least sunscreen and lip balm WITH SPF 15, and better still SPF 30+. The best brand is Banana Boat, which is usually available in Kathmandu.

Moisturizer: A small tube for sensitive or well cared for skins. The air is dry and the sun harsh.

Sun hat:  A technical running cap is ideal. A wide-brim sun hat is also good.

First aid kit: We carry one with aspirin, Paracetamol, Ibuprofen, decongestants, lozenges, various antibiotics for Nepalese varieties of diarrhoea and chests infections, Diamox (an acclimatizing aid drug), antiseptic, antihistamine cream, oral rehydration, bandages and band-aids.You should bring any personal medicines that you need, and if you have had blisters in the past, a good kit.

Water purification: You can get away without water purification but, especially for a hot trek, it is nice to be independent from the lodges or expedition crew. A bottle of iodine tablets such as Potable Aqua, PolarPure or Couglans can be useful however the most convenient system is the strpen which uses UV light to neutralize bugs in the water. We mostly use to water from the lodges but occasionally take water from the streams. The use of mineral water is discouraged from an environmental point of view, but is available everywhere.

Books: One or two with high swap ability. Kathmandu has some great second-hand book shops.

Money-pouch/belt/inside pocket: Most people find wearing one while trekking is a hassle and keep it buried in their kitbag or daypack. The Kathmandu hotel has safety deposit boxes.

Snow gaiters: Not needed but if you have them, consider bringing them if going above 4000m.

Crampons and ice axe: Not needed for trekking - trekking is walking, not climbing.

Additional gear for camping treks:
Inflatable sleeping pad: Thermarest or similar - for expedition/climbing treks ONLY, not tea-house treks. We provide a sponge foam mattress and if necessary, a closed cell pad, but if you have your own Thermarest, bring it. We also have a few available for rent.

Down booties: A good luxury for chilly evenings, available in Kathmandu.

Evening camp-wear: Around camp you can wear camp shoes, sandals (for non-winter treks) or leather boots. No matter what altitude and what season, it is cool to bloody freezing in the evenings. By far the best clothing is:

+ a down jacket, light or thick, available in Kathmandu. Fleece and layers isn't really enough. 

+ Primaloft pants (hard to find) or thick fleece pants

+ fleece hat and neck gaiter

+ thick sox

+ Nalgene or Aluminum water bottle filled with boiling water

Snacks and nutrition:
You will feel your best with plenty of good food and keeping hydrated. We provide the food and the water. However you will also want wholesome snacks and vitamin tablets. Chocolate, chocolate bars, dried fruit bars and dried fruit are readily available in Kathmandu, but Cliff bars, Power bars, energy gels and the like are not usually available.

What we provide
For camping trips, we provide all the tents, a foam mattress each, all the cutlery and utensils, cooking pots, stoves; candles/kerosene lantern, tables and stools, kitchen tent, dining tent and toilet tent; all the main meals while trekking but not snacks; and the best service we can manage.