After working with laptop for about 5 years (previously I used a desktop PC for about 15 years using IBM PC/AT, Intel 486, Intel Pentium 200 MMX and Intel Pentium III), I collect the following tips when buying a new laptop:
1. Ensure that you are comfortable with the keyboard layout (i.e., the placement of the keys) as well as the size of the buttons (do they fit your fingers?).
2. Ensure that there is an opening on the bottom cover to easily access the hard drive. It is really a pain if you have to disassemble the laptop just to take out the hard drive for emergency back-up or installation because the optical drive does not work. It is also good if there are openings for the memory and wireless card as well, but the hard drive has to be easily accessible.
Below is only relevant for those who want to be free by using GNU/Linux:
1. Ensure that the laptop does not have a hardware switch to turn on/off the wireless device that cannot be controlled under GNU/Linux (e.g., http://kerneltrap.org/node/17160#comment-329813).
And, I have the following wishes:
1. The location of the CMOS battery is accessible (e.g., under the keyboard so that only few screws need to be unscrewed). This is very useful when you need to completely reset the machine although perhaps not everything is reset (c.f. http://www.pwcrack.com/bios.shtml).