All these tips are very valid, but at the end of the day, you have to get used to carrying extra weight, no matter how light you get your pack, if you havent carried full gear before, it will take it out of you.. You'll ken what I mean when you're trying to get up the scree on the steep side of Lutharn Mhor from Carn Bhac
I feel like I should restress the not taking any clothes thing.. All you need is what you are wearing plus something warm for the evening.. Winter I take my buffalo shirt, in summer I just take a fleece.
And dont do what I do - spend all my wages on the lightest of gear, only to then chuck 5kg of coal on top for a fire