Many travelers are familiar with this scenario: You are finally going on that well-earned vacation. You decide to take your smartphone on the journey. But you run into a host of tech snags after you arrive at your destination.

You might quickly burn through your cellular data limit, for instance. Or maybe you can’t log in to some apps that send you text messages to confirm your identity. Your maps may not load. And your battery runs out of juice just when you need the smartphone most.

These headaches may spoil what was supposed to be a relaxing vacation. They may even make you wish you had left your phone at home. But your smartphone is your most vital travel tool: You rely on it for navigating unfamiliar places, finding places to eat and things to do, and taking photos.

Fret not, traveler. To help you plan a smooth summer vacation, here’s an overview of the tech you should pack to use a smartphone abroad, and more important, what you need to do with your phone before you depart. (Much of this advice can also be applied to domestic travel as well. If you want to be thorough, click here for a checklist you can print out.)