The Model Trekker

Cooking dal bhaat takes less fuel. Order meals at the same time as other trekkers.
Bring adequate warm clothes so as not to depend on fires for warmth. See that staff and porters are properly outfitted.
Please don't give to begging children. Pay fair prices for food, lodging and services. Buying local products benefits hill economics, but buying antiques and artifacts robs Nepal of its culture.
Carry a plastic bag for litter. Pack out all non-biodegradables and burn papers discreetly.
For Women a mid-calf length skirt or loose pants, and for men pants or knee-length shorts (long pants in monasteries) are respectful of local customs.
Use you head Don't hike too high too fast. And don't trek alone (women or men). Register your name with KEEP or your embassy/consulate.
Be respectful when photographing people. Always ask first, try to establish a friendly rapport, and please don't pay money.
No nudity when bathing please. Women should wear a loongi (sarong) covering them from chest to knees. Don't put soaps (even biodegradable) in streams. Throw soapy water away from streams.
Take hot showers only when the water is heated by non-wood or fuel-saving stoves.
Don't buy bottled water on the trek. Instead, use a canteen or water bottle and add iodine to treat drinking water.
Stick to main trails to prevent erosion.