Not having ever owned a laptop, I'm not sure how valuable my experience will be however...
If you find what appears to be a really good deal on a laptop, do a bit of research before you buy. Try and find technical forums where users of the same model can be found and look around for problems. I currently have a non-functioning Dell for which a class action suit was successfully filed
in the US. This model and others similar all failed shortly out of warranty due to one of a couple of design flaws. You don't want to buy a bargain only to find it is a lemon.
Regularly clear fluff from air vents. Do not neglect this and your laptop will live longer. Excessive heat can shorten the life of the hard drive and can potentially cause ball grid array chips to partially separate from the motherboard (one of the Dell flaws).
Disable as many of the bells and whistles of the Windows graphical interface as you can (ie use the Classic Windows profile). The computer will appear much more responsive as it doesn't have to waste time displaying eye candy.
I hope this is helpful.