Well...This is a good question.
if you want to buy a laptop for gaming, you should look at the cpu speed, ram and video card. Right now the top speed is p4 3.4ghz, 2-4gb ram (2 gig is fine) and 256mb video ram .
p4 3ghz is enough for most of the games, 1 gig ram is enough and 64-128mb video cards will be enough for most of the games.I advise alienware, HP, Sony, Dell , Toshiba. All of these brands have good laptops for gaming.

if you want a laptop for travel reasons you should look at small laptops like 11 inch, 9 inch, 12 inch etc.. Another important issue is battery. You should look at high capacity battery at least 4 hours

if you want a desktop replacement you should look at LCD size, 17 inch laptops will fit you.

if you will  use it  for both travel and games you should by 15.4 or 14 inch laptops. the video card will be an issue , you should look at at least 64mb video cards