I've been fortunate enough to travel a fair bit and from a young age, but for many people if they're travelling for the first time, especially to a foreign country where the language and culture is different from home it can be a bit over whelming. So some of my tips for first time travelers:
It's one of the things I've been able to pick up when travelling in the Pacific Islands. Be patient, don't expect everything to run to a schedule (even if there is one printed), don't expected everyone to understand your stilted Spanish or your frantic hand signs and don't be surprised when things aren't the same as at home. Relax, your on holiday!
I've seen many travel articles where people say put everything you think you need and then halve it. I've never had this issue, and generally travel with the same for a 1 week trip vs a 6 week trip. How? I only take what I truly need, I pack clothes for about 4 days and then wash on the go (have you never noticed the repeat of outfits on this blog) and I travel for comfort.
Learn key phrases
DH and I suck at foreign languages I tried to learn Mandarin in my younger years and it either gets greeted with giggles or looks of disgust. The thing is I am trying and those few key phrases can help break the ice (if you get the giggling response). If all else fails take a small phrase book.
Leave your comfort zone
I'm an overly organised person, too much perhaps. But when I travel I sometimes just have to go with the flow. For others it's trying a new dish, or talking to strangers or dealing with bugs in the jungle. Whatever it is take it as all part of the travel journey.
Respect the local customs
I've seen it on every trip. The women who go with their shoulders uncovered to temples and then mutter under their breaths when they're refused entry. The men who want to be able to drink in public during Ramadan in Muslim countries. Sometimes it is hard to know what the don thing is in each country, customs in one part might be different in another. But do some reading before hand, speak to others that have traveled there and when in doubt when a local says make sure you shoulders are covered in the temples of Siam Reap, don't debate with them why you feel that's an outdated practice.
We've been lucky and never needed it, but we purchase it on every trip. You hear horror stories of broken legs costing 10's of 1000's of dollars, of getting hit by another driver in your hire car and still being slugged with the cost or natural disasters hitting and the trip being extended with no way to fund it. Don't risk it, either purchase travel insurance or make sure your home insurance covers you overseas (I think some US companies do).