Once you figure out which category of laptop best suits your needs, it's time to examine the specifications. You'll have to choose from among a host of options for the processor, RAM, graphics, display, and other features. Deciding what you need and what you can live without is difficult, but it's essential to selecting a laptop you love at a price you can afford. If you don't understand the specs, you could save money but miss out on the features and performance you require, or you could spend too much for things you don't really need.
The CPU is the heart of any computer, and is responsible for running the operating system and every application you use. A speedier CPU means faster-running programs, but usually it also means lower battery life and a more expensive laptop. Nearly every laptop has a CPU from AMD or Intel.
If you're buying a netbook, you're bound to find that it uses an Intel Atom processor. You won't encounter a particularly noticeable difference in performance between the Atom chips you find on modern systems, but the newer N450 Atom processors do offer slightly better battery life.
Ultraportable PCs generally use low-voltage AMD or Intel processors. These chips are usually dual-core CPUs that are quite similar to the regular notebook CPUs found in larger laptops but run at much lower clock speeds (1.2GHz instead of 2.1GHz, for example). Lots of processors--too many to list here--are available in this group, but when you're shopping, you can follow a few general rules: More cache is preferable, and higher clock speeds are better but will drain the battery a little faster. AMD's CPUs are a bit slower than Intel's, but are priced to move. Note, too, that some ultraportables don't use low-voltage CPUs, and are considerably faster (but have shorter battery life) than those that do.
All-purpose and desktop-replacement laptops offer both dual-core and quad-core CPUs in a range of speeds. Intel's Core i3 and Core i5 CPUs are excellent for most users; only people who truly need a quad-core CPU (for encoding video, playing games, or running engineering applications, for example) need to look for a quad-core Core i7 processor. Again, more cache and higher clock speeds are better, but any CPU over 2.0GHz is fast enough to handle all the basic stuff, like playing music, surfing the Web and playing Web games, displaying online video, and managing e-mail.
You'll still find many laptops on sale with Core 2 Duo CPUs, which are the previous generation of dual-core chips from Intel. These models are perfectly fine for most tasks--just avoid the ones with low clock speeds and small caches (1MB or 2MB), if you can. Be wary of cheap laptops bearing Intel Celeron or Pentium CPUs, or those that carry AMD Sempron CPUs; these processors help laptop manufacturers keep prices low, but they do so at the expense of performance.
The GPU (graphics processing unit) in a computer is useful for more than just playing games. This bit of silicon is ultimately responsible for everything you see on screen, from 3D games to the basic desktop. Perhaps more important for some people, many GPUs can accelerate video decoding: With the latest version of Adobe Flash and the right GPU, Web videos from Hulu or YouTube will run more smoothly and look better (especially if you have a netbook or an ultraportable laptop with a weaker CPU).
Most laptops are available with a choice between integrated graphics (from Intel or AMD) or a discrete GPU (from nVidia or ATI, the graphics division of AMD). Integrated graphics are built into either the system chipset (the "traffic cop" that controls the flow of data in the system) or, in newer systems, the CPU itself. They share the main system memory with the CPU. Discrete GPUs are individual chips that are dedicated solely to graphics and have their own pool of memory, which results in far better performance.
Integrated GPUs from Intel are generally quite poor: They don't run 3D games well, and their video decoding is lackluster. The GPUs built into the new Core i5 CPUs are much better than previous integrated graphics, but still not as good as ATI or nVidia dedicated graphics. If you want to play games other than the occasional Web-based diversion, you probably want discrete graphics. You'll find lots of graphics chips to choose from, but in general the 5000 series from ATI is faster than the comparable 4000-series models, and the 300 series from nVidia is faster than the comparable 200 series. Within each series, the more expensive models are speedier: ATI's Mobility Radeon HD 5850 is faster than the Mobility Radeon 5650, and nVidia's GeForce 330M is faster than the GeForce 310M, for example.