Amazon's Prime Day is 4 days this year, and Walmart is fighting back with a week of deals of its own. How to score the best bargains this year.

What started as a simple one-day summer sale at Amazon has morphed into a week of deals at major retailers. Here is what to look for to find the best savings.

In one corner is Amazon Prime Day. Amazon will run four days of sales, starting on July 8 and running through July 11. In the other corner is Walmart Deals. This event also starts on July 8 but, unlike Amazon, it will go through July 13, giving shoppers two extra days of deals.