When pulling together my Budapest packing list, I wrote down what I'm going to be getting up to; how much walking, the different types of activities I'll be doing, what the weather may throw at me, and even consider getting stuck for an extra night. That way I'm not just looking through my wardrobe thinking, I like that, I'll take it - but making it more specific, space saving for a small cabin bag allowance, and planning mix & match outfits.