If you are going to buy from Dell or HP just shop online. Keep in mind that Laptops may take longer because of parts shortages. Look for package deals. Often Dell has deals that are one price one day and then $200.00 less the next day. Try not to buy the cheapest model they have. Look at prices every day for two weeks. Sooner or later you will see some better deals pop up. Often the monitor if sold with the computer has a lower price if sold separately. Just double check to make sure! So have your money ready, pay down your credit card and be ready to strike.
So what kind of computer you looking for?
Laptop, Desktop, Games, E-mail, Web Browsing, Photo Editing, Copying Movies, Watching TV's, Printer?, Scanner, IP Phones, Copying DVD's, etc?
Find a local friend to suggest what you should get that acutaly is good with computers. Someone who actually can take a computer apart and put it back together and get it working.
Retail Rule to live buy:
Buy a computer that does what you want it to do out of the box.
Never beleive it can be upgraded later. That is code for "My boss told be to move this model because the newer ones are coming in next month!" This is what I hate about salesmen. They will tell you anything and there is no way to verify it.