The more put together your look, the more likely you are to be treated well by all the officials you have to pass through (especially when traveling internationally).
On your body:
Pants: What is most important is comfort and form. After sitting and standing for hours, you can begin to look like a wrinkled mess. I try to wear a pant that will hold its shape over the long day.
Blouse: Something comfortable and flouncy, that breathes but isn't super thin. T-shirts not allowed.
Love this: Diane von Furstenburg Orange Blouse
Long scarf/Pashmina: Wonderful for fluctuating temperatures in airports & on airplanes, and super light to carry around. Throw it on when it gets cold, throw it off and stick in your bag when it is gets hot, use it as a blanket to sleep with on a cold plane, or roll it into a ball to make yourself an instant in-flight pillow.
Watch: Always important to know the time. If I have a long layover I make sure my watch is synchronized to airport time.
Flats: I see lots of really beautiful women in sky high heels when traveling... if you're one of them,more power to you! Walking in heels for hours can be tiresome and painful, so pack flats. I really think the most comfortable flats in the world are by Lanvin. Zara makes great substitutes.
Jewels: I adore fun jewelry, even if I have to take most of it off during security checks. So worth it.
In your bag:
Magazines: Save my life on flights. I usually tote about five or six around with me.
Umbrella: If you are coming home to Jamaica where you have a lot of open areas to navigate. Otherwise it really isnt necessary.