1.OS. If you don't want Vista (and believe me, you don't), then don't buy a machine with it preloaded. Getting rid of the crabs is easier. Whichever OS you get, buy a full install disc rather than a "Recovery" disc on a hidden partition from some OEM supplier.
It's a personal computer. Don't accept someone else's version of what it should be like.
2.Screen. You like shiny black screens? Very fashionable, especially from Sony and HP/Compaq. They give you eyestrain. Well, they give me eyestrain.
3.Power- Will the LT be used on the road, or taken somewhere and plugged in? If a) Ask about battery life and maybe buy a higher power one if available. If b), forget it.
4.The power connection. This will be connected and disconnected often. I've had two laptops fail because this connection developed a fault. Make sure it's solid.
5. The keyboard. Ergonomics matter here. Go somewhere you can try it first.
6.Screen size / shape. This is the primary factor dictating the size and weight of the LT. If watching DVDs is important, get a screen size to suit and a good graphic card, or lots of onboard video usable RAM.
7. RAM. Back to the OS. If you want Vista, get 1GB or more. Any less and you'll regret it. Get the most you can afford up to 2GB anyway. Above that is probably surplus.
Or demand XP and run with 512MB- 1GB for 2-3x the performance.
8. In fact, demand XP anyway. Or DOS. Anything but Vista.
9. Weight, with charger, case, half a dozen DVDs and all cables. If it's too heavy to carry around the store, don't buy it.
10. Sound. Will you use it to listen to music? If so, either get good speakers and onboard sound, or good headphones.
11. Software (other than the OS). You may want bundled applications. What you probably don't want is constant demands to update the preloaded software or buy new hardware. HP are particularly egregious offenders in this regard. Demand to know EXACTLY what is preloaded. If you don't want it, don't pay for it. Ask the supplier to remove all adware, and make sure he knows what "all" means.
12. Support contract / guarantee. Exactly what's covered , for how long - and will they collect or is transport to repair point down to you? This should include peripherals like cables and the transformer.
In summary- If you know clearly what is wanted, go to a builder and specify what you want- (and don't want)- and pay for it. Off the shelf laptops can be a disappointment because they have / do not have some feature you want or do not want. It's not a cheap toy. Pay a bit extra and get what you want.
Oh yeah- and get a padded backpack if you plan to carry it anywhere. Laptops are getting lighter, but not light.