Clothing

Conditions
As mentioned in the Hazards section the weather is highly variable. This requires flexibility, fine adjustments and appropriate packing.

I constantly try and maintain an even temperature so that I am warm enough to be comfortable but cool enough not to sweat. When clothes drying is potentially limited this latter is especially important. Also to save weight you may not have much to change into.

I kept my rain gear at the very top (under the lid) at all times when it wasn't being worn. I usually have a light fleece beanie and a buff in a handy pocket as nothing helps control temperature like getting your head gear right. 

I only wore the down jacket around camp, and even then was careful to keep it dry. Fleece layers are less susceptible to moisture and the thick fleece with a hood was an especially good choice on this trek. 

Layers
Lots of layers is the answer. Preferably starting with an Icebreaker merino base layer that never comes off outside Stockholm. That's actually better than it may sound. 

Upper body
Icebreaker long sleeved zip top
Sherpa Trekking T shirt
Sherpa light fleece top
Sherpa heavy weight hooded fleece top
Mont Bell Down jacket with hood
OR (Outdoor Research) Goretex Pro shell jacket

Lower body
Marks and Spencer lightweight quick drying briefs
Quechua stretch trekking shorts (I really like these and cycle in them too)
Sherpa trek pants
OR Goretex Pro Alpine pants with full zip legs

Often I wore all four lower body layers. It was comfortable and warm, but that's a lot of zips when you're in a hurry. 

Extremities
Quechua trekking cap
Quechua light fleece beanie
Outdoor Designs windstopper fleece hat
4 buffs (1 of them a polar buff)
Quechua silk gloves
Lightweight fleece gloves (lent to my companion)
Extremities Goretex mitts with heavy duty fleece liners

That last item seemed overkill when packing back in May, until it saved me from frostbite on the summit. My hands were warm, dry and comfortable in these monsters. Well worth it.