1. Always pack a variety of clothing.
Yes, I know it's summer and that means busting out the tank tops and shorts, but you should always pack a jacket, something dressy, and a few longer and more covering articles of clothing. The weather is an unpredictable thing, and you do not want to be caught without something to keep you protected and ready to go. You may also decide you want to go somewhere that has a slightly classier dress code. You'll thank yourself for preparing for whatever gets thrown at you.
2. Make sure to pack slightly more clothes than you anticipate needing.
After years of traveling, this sort of becomes a habit. If you're kind of a klutz like me, you'll be thanking the heavens that you brought that extra pair of shorts when you inevitably sit in a puddle or spill something red all over your beautiful, brand new white shirt.
3. The Dollar Store may just become your best friend.
In the excitement and rush that comes with packing you will bring twenty pair of socks but manage to forget a toothbrush, tooth paste, etc. If you're traveling anywhere in the United States there is likely to be some sort of dollar store close to where you're staying. You can pick up these items for pretty cheap and just throw then away once your trip is over with.
4. Always, always, always aim for a window seat.
Whether you're traveling by car, airplane, train, boat, etc. you will thank yourself for grabbing the closest window seat. You avoid middle person awkwardness, and you get the best view.
5. If you're traveling alone, make friends with whoever you're sitting near.
Most people try to avoid talking to their intimidating seat mate on planes. Don't be like those people. Share your snack. Talk to them. Ask them about why their traveling. Ask where. You'll learn a lot of interesting things, and it will make the time pass much more quickly. This is especially beneficial when traveling overseas.
6. Talk to the locals.
Everywhere you go, even if you've been there before, there is someone who is going to know more about that place than you do. Talk to the locals. Ask them where the best spots in town are. Ask what fun things there are to do. If you're traveling overseas, ask about culture. Take this trip as a learning opportunity.
7. Be respectful.
If you're traveling with other people, listen to the things that they want to do. Make compromises so that everyone leaves the trip satisfied. Don't let one person dictate the entirety of the trip. If you're traveling alone, make sure to be respectful of the people around you whether that be your flight attendant, your fellow passengers, the area's locals, etc. No one ever complained about someone being too pleasant.
8. Take pictures, physically and mentally.
The most common thing you see when encountering tourists is the immense amount of photos that are being taken. People stand in ridiculous poses and do the craziest things in order to get the most perfect picture. Remember to photograph things other than just the big touristy attractions.
However, don't spend so much time behind a camera that you don't take in the experience. Put everything down for a bit and just soak it in. Pictures may be physical tokens of your trip, but memories bring meaning to your travels.
9. Be prepared to answer a ton of questions upon your return.
Everyone is going to be curious about your trip. Pick a few key stories to tell because you will tell them over and over and over again.
10. Enjoy yourself.
That's what traveling is all about.