For big ticket items, you can compare prices and in some cases, get alerts when prices have dropped. Try BizRate, PriceGrabber, Shopping.com, Yahoo Shopping and Nextag.
Pass on extended warranties if your research shows low repair rates.
Get as many of these as you can when you purchase a car: low interest rates, cash back, and special lease deals. (Sue's suggestion: Consider insurance costs in your decision--different models might have different rates).
Select cruises that don't involve expensive airline tickets to get to the port. And Early Saver programs can cut the cost as much as 30%.
Look for hotel bargains in cities that formerly served as convention sites.
Don't buy more than you need. For instance, a 6-megapixel camera is great for most photos. You don't need to spend more on more pixels.
Maintain a stellar credit score if you plan to purchase real estate (and take advantage of house bargains galore).
When purchasing washers, dryers, ovens and ranges, and refrigerators, consider only energy-efficient ones to save on your utility bills.
Secondhand stores are my personal favorites for clothes.
Finally, for greater discounts at many stores, ask the salesperson if he/she can "work" with you. Negotiate also on shipping, delivery and installation. Paying in cash can save the merchant for a credit-card transaction--so see if the store will pass along the savings to you.
Find more about discount shopping at 50somethinginfo.com.