Screen size: Subjectively, 14” is the sweet spot in balancing screen real-estate and weight. If you aren’t planning on porting the thing around too much, a higher size is probably alright.
Memory: If you’re getting Windows 7, 2 gigs minimum, 4 gigs recommended.
Hard Drive: 300ish gigs, 5,400 rpm is alright for day-to-day, if you need more performance 7,200 rpm. If you’re feeling fancy, and want to go balls-to-the-wall all out on storage, SSD’s are awesome, yet still pricey as hell for any reasonable amount of space. I may get one myself, thanks to the governments of Quebec and Canada giving me back my own money (yay tax refund).
Everything else (Bluetooth only if you need it, wifi is mostly included in all modern day laptops, webcams generally come standard) is pretty generic on most common-use “I want to surf the net and view multimedia” machines. Things such as screen type (eg. backlit-LED) only come into place for techno-nerds (go me) or professionals who need (or want) higher quality screens.
Generally, you’ll want to test out the laptop (yes, by going to a *gasp* physical store), and read reviews prior to the purchase. Different laptops have different keyboards, and provide varying screen quality. The only way to know if the laptop is a good fit for you, is really to try it. Sites such as notebookreview provide a wealth of information through reviews and quality user feedback which can generally be found in their forums. Don’t take all the comments posted online at face-value, I have no doubt companies promote their products in forums, posing as consumers. Also realise that sometimes, the most vocal people in forums tend to be those who have had problems.
As to build quality, I’m a recently converted die hard ThinkPad fan (now from Lenovo). Generally, HP/Dell/Toshiba will all provide comparable quality laptops, below the $1,000 price point. I’ve heard people complain about the reliability of their Dell Inspiron / Vostro laptops (dying power adapters seems to be a common one), but then, this may entirely be anecdotal (small sample size), and Dell may provide high quality machines. If I had money to blow, Alienware or Voodoo would probably get my money, but those are definitely “luxury” buys. As to Apple laptops, I’ve used them and they generally have great build quality (avoid first editions / releases of new models), though ultimately, I refuse to pay the mac tax.
I hope some of this may prove useful and happy laptop hunting,