1. Pick a size
Perhaps the toughest question to answer is what size tablet to get. Models like the Amazon Kindle Fire HD, Barnes & Noble Nook HD, and Google Nexus 7 have 7-inch screens, while the iPad Mini stands a little larger at 7.9 inches (diagonal measurements, all). The Kindle Fire HD 8.9 and Nook HD+ measure 8.9 and 9 inches, respectively, while Apple's flagship iPads have 9.7-inch displays. Microsoft's new Surface RT leads the pack with its 10.6-inch screen. (For purposes of this story, I'm not covering business-oriented tablets that also double as laptops with compact Laptop Keyboard .) Obviously bigger is better when it comes to things like browsing the Web, watching movies, and playing games. But a bigger tablet is also heavier and harder to hold single-handed, and I find it too unwieldy for things like reading in bed. That's why I tend to look at 7-inch tablets as more practical. I like the portability (I can tuck one into an inside coat pocket), the lighter design, and especially the price: most 7-inch models start at around $199.
2. Know your wireless options All tablets offer Wi-Fi, meaning they can connect to the Internet when there's a nearby hotspot (like at home, the office, a coffee shop, etc.). But what if there's no Wi-Fi and you want to, say, browse the Web or listen to Pandora? For that you'll need a tablet with 3G/4G capabilities, which limits your options somewhat. Indeed, as of this writing, only the Google Nexus 7, iPad, iPad Mini, and Kindle Fire 8.9 4G LTE Wireless are available with a cellular data option. Going that route not only bumps up the price of the hardware, but also saddles you with another monthly bill for service. (Prices vary depending on carrier and plan.)
3. Pick a platform
When choosing a tablet, sometimes it's best to factor in the smartphone you already own. Do you have an Android phone with compact Laptop Keyboard ? It might make sense to opt for an Android-powered tablet like the Google Nexus 7 or Nexus 10. Likewise, iPhone owners may be happiest with an iPad, while the three or four Windows Phone users out there should probably look hard at a Microsoft Surface tablet. The idea here is to stick with your existing "ecosystem," as you've probably already invested in various apps, games, movies, songs, e-books, and the like. If you switch platforms, a lot of that stuff won't transfer (i.e. the movie you bought from iTunes won't play on a Nexus, and the copy of Angry Birds you bought for your Kindle Fire isn't compatible with the iPad). Ecosystem allegiance is not only the convenient choice, but also the thrifty one.
4. Choose your features
Tablet makers love to crow about their HD displays and super-high pixel density, but the reality is that all tablet screens look pretty great. I'd argue that size is a more important consideration than resolution. If you want the option of snapping photos and/or making video phone calls, make sure to choose a tablet with at least one built-in camera--a feature you won't find in models like the Kindle Fire or Nook HD. One potentially important consideration is expansion: some tablets have a slot for inserting inexpensive microSD cards, which can expand your available storage space for things like music and movies. Unfortunately, iPads don't, and neither do Amazon's Kindle Fires. Also, if you're interested in using your tablet for navigation, look for built-in GPS capabilities--keeping in mind that some models require the aforementioned 3G/4G option, which assists the GPS in determining your location.
5. Know your accessories
You can tell a lot about a tablet by what accessories are available for it. For example, you'll find countless cases, keyboards, screen protectors, and the like for Apple's iPads and Amazon's Kindles, which have the benefit of being the market's biggest sellers. But these kinds of extras are fewer and farther between for the likes of the B&N Nook, Acer Iconia, and Lenovo IdeaTab, meaning you won't find as many options. In other words, before you choose your tablet, make sure any accessories you might also want are readily available, just so you don't face any unfortunate surprises later. And if your tablet doesn't have Bluetooth capabilities, it won't work with most third-party tablet keyboards, to say nothing of Bluetooth speakers (which are always a great add-on).
One final piece of tablet-buying advice: steer clear of dirt-cheap, no-brand tablets. They may have tempting prices, but often they're incompatible with a lot of the most popular apps--and there's no way to know which ones until you try to install them from the included app store. Where tablets are concerned, apps are everything.