Size

Laptops come with all sorts of different screen sizes, from 12-inch to 19-inch versions. The greater the screen size, however, the heavier and bulkier your laptop will be. A heavy, bulky computer is undesirable if you travel frequently and need to take your laptop with you.

Basic Needs

Your laptop needs features that anticipate the future. For example, if the typical laptop of today has 100 gigabytes of storage capacity, consider getting one with 30 percent more storage in order to compensate for future needs. If you want to work with media, make sure you get one with detachable and attachable media (DVD/CD) drives.

Battery Life

One of your biggest concerns, especially if you are a mobile person, is the battery life of your laptop. Estimate how much time you expect the laptop to stay on at one stretch, and add about half an hour or an hour to that estimate to determine how much battery life you want your laptop to have.

Features and warranty

Consider any other features that are important to you in a laptop, such as image clarity. And spending a little money on an extended warranty will buy you peace of mind if something goes wrong with your new laptop.

Expert Insight

Do not judge a laptop's central processing unit, or CPU, by its clock speed. There are many other factors that affect how quickly a CPU will function. Pay particular attention to the laptop's floating point operations per second, or FLOPS, which some experts consider a better measurement of a microprocessor's speed.

Source:

Webopedia: What is FLOPS?