Multitask like a pro
Multitasking on the iPad has improved immensely thanks to iOS 10 and 11, and it's crucial for doing real work. There are two main multitasking layouts in iOS: Slide Out and Split View. To use either, open your first app, put the iPad in landscape mode, then drag up from the bottom of the iPad's screen to show the dock. Tap and hold the dock icon for the second app you want to open -- if it isn't in your dock, you'll need to open it first so it appears in the Recent Apps section on the right -- and drag it upward. Dragging the icon to the middle of the screen will invoke Slide Out, which displays the second app on the right side of the screen on top of your first app.
Dragging the icon to the right or left of the screen, however, invokes Split View, which in our opinion is far more useful: It opens both apps side by side, letting you split the screen 50/50 or 25/75 between your two apps. To exit Split View, drag the slider to the edge of the screen until one of the apps disappears.
This alone makes it much easier to do work on an iPad. You can read in one app while writing in the other, or have a calculator open to the left of your spreadsheet. In many apps, you can even drag and drop items between them by tapping, holding, and dragging. For example, you can drag photos from the Photos app to a new message in Mail, drag a link from Safari into your Notes app, or drag a contact from the Contacts app into a message. Some third-party apps support this and others don't, so you'll just have to try it out to see where it works.
Use web apps in your browser (instead of mediocre mobile apps)

The iPad has a lot of polished apps, and some of them work perfectly with the device propped up on a desk. But many aren't designed for laptop-like usage; they're designed for touch. Microsoft's Word app for iPad is good, for example, but the web version has easier text selection and many more formatting options in the toolbar, so you don't have to tap through menus as much. (Google Docs has similar advantages on the web, though as of this writing, the Google Docs web app was broken on iOS. We have some questions about its reliability.)
Most of us inherently gravitate toward apps over websites, especially on mobile devices. But native apps aren't always better: Sometimes the web version of a given tool will be more robust and easier to use.
Just make sure to request the desktop version of the site and not the mobile version, which is usually just as hampered as the mobile app. In some cases, visiting a site on an iPad won't even give you the web app; it'll just direct you to the App Store. Make sure you use your browser's "Request Desktop Version" feature to get the most laptop-like experience on any web app you use.
If all else fails, use your iPad as a second monitor

Let's be honest: The iPad can't do everything (as much as Apple might want you to think so). For some tasks, you'll have to suck it up and use a real computer for maximum efficiency. But that doesn't mean your iPad becomes useless. In fact, with a simple app and a Lightning cable, you can turn your iPad into a second monitor for your laptop or desktop.
Duet Display costs $10 and is well worth the price if you want to add some screen real estate to your laptop. Just buy it on your iPad, download the companion program to your Windows PC or Mac, and start both up. Plug your iPad into your laptop using a Lightning cable, and it should automatically detect your PC and extend the display for you. You may need to adjust Duet Display's settings on your computer for the best-looking results.
Images: zhengzaishuru via Getty Images (Tentacles); Richard Lai / Engadget (iPad as display)