Many laptops, particularly "business" laptops, have a numeric keypad crammed in on the right-hand side of the keyboard. If you don't need or want the keypad it can be quite annoying, so look for a laptop that has only the standard QWERTY and function keys.
Feel is also important. Some keyboards feel cheap while others feel smooth and precise. Some are noisier than others.
Some laptops have full-size arrow keys while others have arrow keys that do double-duty. They become the Page Up, Page Down, Home, and End keys when you hold down the Fn (Function) key. Some laptop keyboards shrink the arrow keys to less than half the size of a normal key to save space.
If you're used to having a separate key for each function, look for a laptop that has a similar keyboard layout. You can get used to pretty much any keyboard after using it for a while but make sure to get a laptop you can return if you really don't like the keyboard.
What should I know about touchpads?
Windows installs a default touchpad (or trackpad) device driver that soft of works but has bare-bones functionality and isn't precise. A jumpy touchpad can make you crazy. Touchpad manufacturers usually have a downloadable device driver that's much more precise and allows programmable, multi-finger, multi-directional strokes. Some drivers allow you to disable or desensitize the touchpad when using a mouse so that your palms don't move the cursor unintentionally while you type.
What should I know about USB ports?
Make sure your laptop has USB 3.0 ports. If you have USB 2.0 devices, don't worry - they work just fine if plugged into a USB 3.0 port - just more slowly.
If you have more devices than ports, get a USB hub. It's a good idea to have a large, powered hub for use at home and a small, non-powered hub for traveling. (Some laptops have built-in powered USB ports.)
USB Type-C is a new, smaller physical connector. It's not in widespread use yet so you won't need Type C ports for a few years.
What should I know about video ports?
Most newer laptops and monitors have HDMI ports, just like the ones on your TV and DVR. If you're planning to use an external monitor with your laptop but can't use an HDMI cable, you'll probably need a mini-display port adapter. They're inexpensive and you can get ones that connect to VGA and DVI monitor cables.
Laptops usually have function keys that allow you to switch from the built-in screen to an external monitor, or to extend your desktop onto both screens.
What should I know about wi-fi and Bluetooth?
Like everything else, the quality of your wi-fi and Bluetooth connectivity depends on your needs. If you travel, you want a laptop that can maintain a good wi-fi connection even when your hotel room is at the far end of the boondocks. In some laptops, you can have an upgraded wi-fi card installed. They're not expensive and very easy to replace so find a technician who doesn't charge you an outrageous fee for ten minutes worth of work.
What should I know about power supplies?
Power supplies (aka AC adapters, bricks, etc.) can fail. It's best to get a genuine replacement. There are cheap knockoffs available that may or may not work well with your laptop.