I pack things that I am actually wearing, tested and proved. I second La Belle Demimondaine's suggestion for jewellery and may I add accessories: these are what will "feed" your creativity as days advance and you find yourself with the same pieces. Belts are very important for me, as they can change the way an outfit looks. But also clutches and purses - I always bring more than one, and often buy one on the trip too!
First and foremost: look at the coats/outerwear you are bringing. Can you create quickly and simply 2 or 3 different outerwear outfits? Does everything make you happy? Can you wear the purse(s) you are bringing with each one? Does the footwear agree with every one of them, in terms of colour, but also shape and leg length?
To decide on colours for your capsules, go from your toppers down. Which toppers are you bringing? Then the maximum number of tops that will go with these toppers, then a few very versatile bottoms that will go with almost everything.
Footwear is also very important, as it could make or break an outfit. AND for comfort. When travelling, we often must walk more than usual so bring 8hr shoes/boots. If you create a great outfit with 2hr shoes, you can be sure you'll end up not wearing that particular outfit. I know you probably know, but just a reminder.(It's a mistake I often made). I find that when I do this, it leaves me less choices on what to bring, which is a bit depressing but at the same time makes it easier. (I also know better what I really need!).
If you are bringing dresses or skirts, pay special attention to what you will wear on your legs and if it matches your footwear (including boots if you need them where you are going) and if you feel comfortable in them. I like to bring dresses that can serve as tunics over jeans or pants or leggings as well as being worn on their own with either tights, nylon or nothing.
