An important aspect of laptop selection is reliability over time. We repair laptops and have seen an average of 10 a month since 1992... Inexpensive laptops are frequently more trouble because the manufacturer has to compromise somewhere... usually the screen, and cooling fans.
Avoid units that are designed to be too pretty. Look for those that offer a long warranty as an option.
We have seen the best laptops are IBM/Lenovo Thinkpads, Toshiba Techra (but support is bad and parts are hard to get), HP in the upper price range, Dell or Gateway in the upper half of their price range.
Sony is among the worst because of the inability to get parts when they fail, and the early failure rates. Compaq, though getting better, has been more trouble than Compaq, eMachines fail way too often, as do Alienware units. We like Gateway, Dell Latitude, higher priced Dell Inspirons.
If you intend to use the laptop as a gamer, you are asking for trouble.
The less expensive laptops have high failure rates of the LCD screens or the screen inverters.
No-Name or off-brand or unknown makes are a bad choice at any price because you cannot get parts when they fail.
I would avoid low priced Compaqs, Sony VAIO, Alienware, eMachines, and Toshiba because of parts and service. Do not buy online unless you have seen the machine to assure it has plenty of cooling fans and air vents...
A lightweight laptop is a bad choice unless it is an expensive Dell, IBM Thinkpad or the like... as it is more costly to build a lightweight unit.
Good luck.