Checklist to buy a new Laptop

The above mentioned criteria (usage goal of device and budget) are from my perspective the most important and you will certainly find a mobile computer which will fit your need. But to be absolutely sure you may want to consider some other factors.

Operating System

There are about three popular operating systems. One is Microsoft Windows, the other Mac OS X and the third would be a Linux distribution (which you can obtain free over the web).
For the purchase decision, I think you should just look at Windows and OS X, the other is anyway free and runs, supposed enough patience, on every machine. The actual version of Windows, which is Vista, needs a lot of memory (RAM) and has some features I do not like. OS X on the contrary, allows you to run even Windows an Apple machine (Boot Camp is included for free and VMWare or other can be bought for little money).
This is for me a clear indicator, that OS X is the much better choice. The only reason not to choose Apple would be a low budget, since Mac is a little bit more expensive (but also with more benefits), or the case that you need a certain Software on Windows (even this should work with virtualisation), or at last you do not want to learn a new operating system (supposing you are using Windows right now).

Portability

In most cases you will have a discrepancy between performance and portability. The smaller a computer is, the less performance it has and vice versa. This is at least valid until today.
There are different categories of laptops/notebooks which correspond the different needs:

• Netbooks: Small devices with tiny displays (between 7" and 10") and also with small keyboards. Used for high mobility and equipped with the most wireless communication standards.
• Sub-Notebooks: Little notebooks with the weight of about 1 to 1.5 kg, a little bit larger displays (10" to 13") than Netbooks. Concepted for the mobile use, but now rivaled by Netbooks.
• Notebooks optimised for Travel/Mobility: Larger display (14" to 15.4"), with the weight of about 1.7 to 2.5kg. Fully equipped notebook with a normal keyboard and most connections.
• Notebooks as desktop replace: Large displays (up to 17") with heavy weights (up to over 3kg), but with large processors. Preferred by people who like to play games or need a lot of processing power.

So this is what you need to know about the different categories of notebooks/laptops, that you can decide which is the right one for you.
Be aware that the size of the device influences always the size of your keyboard, as long as you do not use an external one. So if you have to write a lot, you may want to buy a larger device, with a more convenient keyboard.

Connections

The most new devices support the standard connections you may know from your everyday work with computers, such as USB, Bluetooth, Wireless LAN (WLAN), LAN/Ethernet and an external monitor/beamer.
But as soon as you need extraordinary connections, such as FireWire (my MacBook Pro such a connection that I use for my external hard disk) or Infrared etc, it is getting tricky.
I can give you just the advice to compare multiple devices from the same category, which you may want to buy (e.g. you have looked around and have filtered your first impressions).

Communications

To this topic there I can tell you almost the same like for the last one. You have to look carefully and compare, since many manufacturers produce some models with additional features or you can even customise (e.g. Dell) your notebook completely when you order it.
So this gives you a great chance to select a basic model that fits most of your needs and then adapt it to your personal preferences.

I do not have more hints for you at the moment. Just one last word for now: From my experience, for the most cases a standard configuration from the wholesale or the discounter fits the average computer user's needs. So do not drive yourself crazy when you browse around for your next notebook and look on the internet if there are any ratings (good or bad ones).