Before you even think about putting one clothing item in your suitcase, check the 10 day forecast of your travel destination. Don't get stuck with only sweaters in warmer temps or tank in chillier weather.
I organize by thinking by day and outfit change. A four day trip outfit checklist would look like this (with explanations):
Plane Outfit: this outfit can be recycled for the flight there and back. Yes, recycle your outfits!
Thursday: this is the outfit for changing into once settled in.
Sunday: before getting on the plane, change into your plane outfit.
Extra Underwear: not required, but I like to shower anytime I change clothes so it is a must for me!
What to wear? Dress it up a little! You never know who you may meet and you should want to look your best for the occasion. Put more effort into your day looks and you don't have to pack an
additional night outfit for each day you are there.
You don't need a whole bunch of shoes, you just don't. I used to not feel comfortable with what I packed unless I had options. However, every pair I packed never got worn and I usually rotated the same 2 or 3.
For women: A comfortable walking shoe, a nice casual flat, and a neutral heel is all you need. Throw in a pair of flip flops if you're headed to the beach.
For men: A comfortable walking shoe and a nice casual shoe. Add flip flops for sandy locations.
I have a toiletries bag with pockets for all of the essentials that I never unpack. I just check it to make sure I have enough product to get me through my trip, roll, it up and toss it in my bag. Outside of the obvious items, I keep tube of hydrocortisone handy. Hydrocortisone helps to reduce swelling, itching, and discomfort that can result from a number of things during travel.
While in Jamaica a coupe of years ago, I got bit by some tropical bug and after I few hours I had to go to the on-site clinic at my resort because the pain and redness was getting out of control. $85 USD later, I had a tube of hydrocortisone that could be purchased at your local dollar store in the US.
Other items of note in my bag:
Mini-Conditioner: recycled from a home hair coloring kit
Travel Size Lysol: Can't trust those hotel linens!
Q-Tips: Many uses outside of the obvious.
Lavender Oil: To help relax and rest.
Pumice Stone: For pampering feet after long travel days.
Here is a photo of my actual bag, I've had it for years:
Be sure to pack a book or two. Also, don't pack a charger and a backup charger cord. We know those charger cords burn out eventually and you don't want to get caught without a working cord. Normally you can buy one at a local convenience store, but it's just good to have a backup purchased at a discount from Amazon or Ebay.
Bring a journal. Travel seems to spark great ideas and moments of clarity. Don't miss them!