There are several characteristics of laptops that you have to prioritize based on which are most important:

1. Size and weight.  If you travel a lot, you may want to get a small, light laptop.  However, there are tradeoffs; the smallest laptops are often less powerful, and the larger the screen, the easier it is to read or fit on more information.  It’s usually good of you’re going to be using your laptop as a primary computer to find a tradeoff between small size/light weight and usability/power.
   


2. Battery life.  Battery life often goes along with size and weight.  Larger laptops often have more power-hungry components, including large screens, powerful graphics cards, and even desktop CPUs.  But you don’t need to get a small laptop to have one with a long battery life, and you aren’t guaranteed a long battery life if you get a small laptop.  For example, the four-pound, 12” widescreen Dell Inspiron 700m with its lower-capacity four-cell battery gets around two and a half hours of battery life, whereas the eight-pound, 17” widescreen Dell Inspiron 9300 gets as much as four hours with it’s higher capacity nine-cell battery.
   


3. Screen size and resolution.  It’s nice to have a big screen; at low resolutions, it’s easier to read, and at higher ones, you can fit much more on the screen.  It’s also nice for when you’re watching a DVD – who wants to watch it from across the room on a 12” screen when you can do so on a 17” widescreen instead?  Just keep in mind that you will pay a price in overall portability.  I had a 17” widescreen that weighed nine pounds and barely fit into one of the trays at the airport security x-ray machine (don’t forget that you have to take out your laptop each time you pass through security) – as 19” and even 20” laptops come out, size is a serious problem to consider if you plan to carry your computer anywhere outside your house.  At the other end of the scale I had a 10.6” widescreen and a 12” widescreen; both of them were a bit on the hard-to-read side, and the keyboards were cramped, but on the plus side they were light and small, and thus very easy to carry around everywhere I went.
   


4. CPU and graphics processing power.  If you get an ultraportable-style laptop, chances are that you will get a special low-voltage CPU that will be slower than most other processors.  On the other end of the spectrum, the most powerful laptops have desktop Pentium 4s and Athlon 64s, but you will pay the price in terms of weight, heat, and battery life.  The compromise is a normal laptop processor (the different types will be discussed further on in this article).  Graphics processors also vary in power, from Intel and ATI integrated graphics (with similar performance to integrated graphics on desktops), through midrange graphics processors that perform decently but don’t generate too much heat or suck up too much power, to the highest-end processors available in gaming laptops that have much the same effect as desktop CPUs on battery life and heat, but perform every bit as well as their desktop GPU counterparts in games.
   


5. Specific needs.  Do you need to plug in a serial or parallel device?  Most laptops don’t have serial and parallel options available anymore; you will have to find one that does.  How about a PCMCIA card?  Many of the latest Core Duo laptops are switching over to ExpressCard, which is incompatible.  You may also want a tablet-style laptop with a write-on touchscreen, or a multimedia laptop with a FireWire port, a TV tuner, and Windows XP Media Center Edition.

These miscellaneous criteria will all play a role into what type of laptop you will get.