From the main Google Drive interface, click the cog icon (top right), then Settings and General: Tick the box labeled Create, open and edit your recent Google Docs, Sheets and Slides files on this device while offline and the sync begins.
Gmail for Android and iOS actually syncs email for offline access automatically, though you might not realize it—head to the settings for your Gmail address from the main app menu then use the Sync Gmail and Days of emails to sync options (Android) or the Sync settings option (iOS) to manage this.
If you’re a Google Docs, Sheets, and Slides user, you can get files created in these apps to cache locally in Chrome, just in case something happens to the cloud servers (or your internet connection).
The offline playback option is less common in video streaming apps on the desktop, so you’re probably going to have to rely on phones and tablets to sync movies and shows for watching if streaming isn’t available—it’s a good idea to have at least a few hours of entertainment available offline, just in case.
Even if you spend most of your time managing your email inside a web browser, it’s still worth keeping your messages in sync with a desktop program as well, just in case—both Windows and macOS have basic, built-in Mail apps that will sync your messages locally, or you can use something like Thunderbird.
This might mean keeping copies of important files on an external disk drive or a NAS drive, for example—we’ve written before about how useful NAS drives can be, because they as your own personal cloud on your home network.
You’ll find the feature in just about every music-streaming app, provided you’re a paying subscriber—it’s the little blue cloud download icons in the Apple Music desktop app, or the Download toggle switches at the top of every playlist in the Spotify desktop app, for example.
In the case of OneDrive on Windows, if you right-click on the OneDrive entry in File Explorer then choose Settings and open the Settings tab, you’ll see a Save space and download files as you use them option—turn this off to store all your files locally.
Most cloud storage services now make at least some effort to free up space on your computer by keeping certain files exclusively on the web and only downloading local copies when you actually need them.
You can enable offline Gmail in Chrome by clicking Settings (the cog icon on the right) then See all settings, Offline, and Enable offline mail (you can choose how many days of email get cached).
While sending and receiving emails obviously isn’t going to be possible if your email provider of choice goes down, you can at least make sure that you’ve got copies of your emails so you can still do some inbox sorting and draft some new messages. Gmail is good at this.
After following the cloud storage tips above, make sure you’ve got your work accessible offline wherever possible.
Your best option here is actually the TV app on macOS, which is still iTunes on Windows for the time being: If this is where all your media is stored, you can click the download button (the cloud and arrow symbol) next to any show episode or film to store it locally.
The most recent versions of the Microsoft Office apps will encourage you to save to OneDrive for syncing purposes, so make sure your local files are actually stored, or save them in a separate folder as well.