After traveling in Japan for the past two weeks, spending only two days at a time in a city before flying, driving, or taking the train to the next one, I’ve learned quite a bit about what it takes to travel as an adult. Among organizational skills and common sense about staying safe and respecting local culture, I’ve found that the most valuable skill when doing some heavy traveling is packing effectively and efficiently.

These are a few packing tips:

1. The weather app is your greatest resource.

Before you even begin tearing your closet apart to fill your suitcase, take a look at the weather forecast for the entirety of your trip. This is always subject to change, so I would check with a few other sites as well for the most accurate picture of your forecast.

2. Pack underwear first.

This is the first thing you will forget, and the greatest regret you’ll have.

3. Organize by sorting.

I’ve found that the best way to ensure you aren’t forgetting anything is packing by grouping. Go through each area of your room and take from those places exactly what you need—then lay it out so you can see it before you put it in your suitcase. I use my dining room floor to organize everything on, but this risks my dog walking over all of it and stealing my underwear that I find buried in the backyard three weeks later. When you can see everything you need by category (T-shirts, pants, toiletries, electronics, etc.), it is easier to determine what can be left behind and what you’re missing.

4. Consider what you need for your day of travel.

As obvious as it may seem, leave all the items you’ll be using on your date of departure out of your packed bag and in an obvious place you won’t leave them. I have a tendency of putting a pile of clothes, a toothbrush and hair straightener, and my phone and computer chargers on the dining room table. It drives my mom up a wall, but I never forget to throw these items in my carry-on.

5. Consider TSA/other security regulations.

You want to make sure that you’re traveling with everything you need, but don’t forget there are some very specific requirements for everything you packed. Weigh your checked bags so you don’t get overcharged, and double check your carry-on dimensions to make sure it isn’t too big. Don’t forget the limit for fluids going through security (this varies in different countries), and remember that items like lighters, weapons, illegal drugs, black-market organs, etc. won’t fly.