First of all decide what exactly do you need Business work, Home use or entertainment only after this you can go for configuration.
Set you budget so that your valuable time will be saved by avoiding search of products which are out of your budget.
After that decide what exactly do you want about these main components of a product
Screen Size
CPU
RAM - primarily memory
Hard Disk
DVD Writer
USB ports
latest connectivity ports
Battery life
Web Cam
Security Options
Weight
Touchscreen or normal
TouchPad Quality
After this search online but search price in market also.
Take your time to compare and Decide which one is the best for you.