The destination and mode of travel are part of my packing strategy, but generally, I travel for leisure. This approach works well- I pack two tops for every bottom, bring a mix of bottoms some of which are quick to dry, easy to spot clean, bring things that are casual yet dressy, like a long linen skirt in summer- something that works for a dinner date is about as fancy as I get, and can vary with the weather- leggings for colder nights under long skirts are an easy add. I always pack a swimsuit (you never know when an onsen spa, pool, or water park will be on your agenda), a scarf, and a jacket or blazer (to dress up pants and add a layer of warmth).
To keep it organized, roll together the top, bottom, and any undergarments needed. Pack the rolls tightly into a bag or suitcase. For kids or those who struggle with staying organized, use a rubber band around each outfit which helps with counting outfits packed, plus later when the suitcase explodes, and for some reason this always happens to my children's bags, anyone can discern what's clean (still has a rubber band around it), what goes with what (still has a rubber band around it), and when they're out of clean clothes (it's all chaos). Also roll up pajamas with fresh underwear. If you have nylon stuff sacks, fill them with additional undergarments such as socks, tank tops, and panties. Vary the extra tops to flex your choices for hotter or cooler weather by packing thinner or thicker fabrics and longer or shorter sleeves.
Sometimes trips have a unique purpose such as a bike or ski trip requiring special clothes, add those items. For example, on a beach trip add a coverup and flipflops. For a big city trip, add a dressy pantsuit- mainly because I hate to be cold or underdressed.
For accessories, I tend to go with beaded necklaces, a pair of sandals (plain black Chacos), and a pair of closed toe shoes (varies by trip). If the clothes' colors match or compliment each other, it simplifies everything.
I also try to pack minimal toiletries, however, I prefer my own razor, hair conditioner, hair goop, skin lotion, and toothpaste.
For carry on items, I go for both dulling the senses and entertainment. Pack an eye shield, earplugs, a scarf (for blocking light and warmth), a real book, a notepad, pen and mechanical pencil, an empty water bottle, a zip bag with a widget full of audiobooks, headphones, and the necessary cords and plugs for a mobile as well. I also carry the travel paperwork for where I'm going, necessary identification, any medications, Motrin and Tylenol, sunglasses, a small sunscreen stick, eyeglasses, a contact lens holder loaded with saline, toothbrushing items, nail clippers, and extra layers for cold flights like leggings, socks, and a sweater. Though I wear little makeup, I do keep an item or two in my bag along with lip moisturizer.
When my kids were little I always brought a thermometer and decongestants. Now I limit it to band aids of various shapes for the cuts and blister crowd.