I'm assuming you mean things to pack @sophia? I have a checklist of my go-to outfits & essentials in Evernote (ahem, @jennikonner), so that packing is as painless as possible.
  1. First things first: check Dark Sky, the world's chicest weather app, before you pack.
    The worst is when you arrive in a city and realize your wardrobe is inappropriate for the weather. So check Dark Sky for info before you pack.
  2. You need: An organized carry-on bag.
    I try to keep everything in pouches: phone and computer chargers in one, headphones and batteries in another, makeup gets its own, while skincare and hair stuff usually go together in another. Magazines go inside my computer case, as do snacks.
  3. You need: Shoe bags for your shoes AND bags.
    Bless shoe bags, for they have so many uses. I use one for each shoe I'm packing, and pack my alternate handbag/clutch in one too. I also use specifically designated ones for bras, smalls, and tights.
  4. You need: A mini cosmetics case with small amounts of your go-to over-the-counter meds.
    Advil, Pepto, Visine, Cortaide, Bonine, Mucinex. Better to be prepared than not. Also: nail file/mini clippers, floss, toothpaste, bobby pins, safety pin, sealed packet of nail polish remover, double-stick tape, Clorox pen/wipes, baby wipes, q-tips, etc. I replenish all supplies after every trip, so the next time I can just toss the kit into my bag and go.
  5. You need: A travel-sized Downy Wrinkle Release Spray
    Not all hotels have steamers, and this stuff is great in a pinch.
  6. You need: Band-Aid Tough Strips
    I tend to walk more on the road and often get blisters. These guys are the strongest Band-Aids on the market and never come off.
  7. You need: SK-II masks.
    Individually packaged, these pricey-but-worth-it masks deliver the exact amount of moisture your skin needs after a flight.
  8. You need: Roll-on fragrance.
    Le Labo makes travel-friendly roll-on oil iterations of their signature fragrances, which are perfect for trips. Sephora also has a HUGE selection of most major perfumes.
  9. You need: Multi-use clothing in un-fussy fabrics.
    Ideally I try to pack pieces that all play nicely together, so I can mix and match and be appropriate for day or night. That means lots of neutrals (gray, black, navy) with a few bold/print pieces to liven everything up. And I try to pack things that don't wrinkle easily, meaning: sturdier fabrics. That said, silk is easy to de-wrinkle.
  10. You need: A versatile outerwear layer.
    Trench coats are good because they are appropriate for a wide array of occasions. Otherwise a wool-gabardine or wool-blend coat is a good option because it's a pretty seasonless fabric/weight. I also like a leather jacket if I'm not going anywhere freezing.
  11. You need: A day-to-night handbag.
    That said, you can always stuff your shoulder/day bag into your carry-on and pack a pouch/clutch for night. The latter can do double duty as a jewelry case too.
  12. You need: A smart airplane outfit, like lightweight layers in dark colors/prints + dark jeans with stretch or silky, slouchy trousers.
    I often do a three-quarter sleeve striped t-shirt or a dark silky Equipment blouse and cropped black jeans, plus an oversized lightweight scarf in a print and a leather jacket or an army green jacket, depending. All pieces that can do double duty and work with other pieces in my suitcase.
  13. You need: TSA-friendly shoes, like flat boots for winter/slip-on loafers or flats for summer. Chucks are fine too, or whatevs sneakers you're geeking.
    I wear those little mini socks under my loafers so that I don't have bare feet going through security.