I recommend going for a Core 2 duo, or core i series processor.
Make sure its a 64 bit laptop with genuine Windows 7
With a minimum memory of 2gb ddr3 RAM , but nowadays most laptops come with 4gb RAM
And a 500gb SATA HDD

A few laptops come with a good graphics card. (512mb is good enough)

Try to get one with an Extended warranty if possible.

You may find some interesting deals at many websites