Equipment tends to feel more and more heavy with each passing minute, especially at higher altitudes, so carry the bare minimum you are sure you will use. I always try and hire a porter for my two camera bags, but often find that when I need a special lens at a crucial moment, the porter is a kilometre or two behind or ahead Wear a camera jacket or a jacket with several pockets for lenses and filters. A small umbrella or a polythene rain protection sheet will prove useful in sudden showers. Try to carry a tripod along. They can improve your pictures in two ways. First, they stabilise the image, so you can use a smaller aperture, giving you a greater depth of field. Second, you get better compositions with the camera resting steadily on a tripod.