Washington Post published a guide on how to buy an all-purpose laptop.
I would add that you should also buy after-sales support/warranty, like Dell’s 3 year complete cover.
Your laptop is likely to work as hard or harder than you, if you’re the kind that leaves your laptop on all the time to peer-download.
It’s very likely to wear and tear after the first year and the after sales support/warranty protects your investment.

How to Buy an All-Purpose Laptop – washingtonpost.com

Looking for good value in a notebook? Here’s our all-purpose laptop buying guide for the average Joe.