Instructions
Craigslist
Navigate to the craigslist website and click on your specific city under your state. Click on "Video Gaming" under the "For Sale" section and click in the "Search For" text box.
Type in "Nintendo DSi" into the text box and enter a minimum and maximum price. Set the maximum price no higher than $140 or it will defeat the process of trying to find a cheap Nintendo DSi, as the normal retail price of a Nintendo DSi is $150.
Click on the "has image" box to search for Nintendo DSi posts that have images. Click on the "Search" button to search the available listings.
Click on the specific Nintendo DSi listing that you would like and read the advertisement. The contact details will be listed in the ad. Contact the seller to buy the Nintendo DSi.
Amazon
Navigate to the Amazon.com website and click in the text box. Type in "Nintendo DSi" and click the "Go" button to search for the DSi.
Find a Nintendo DSi listing and look to the right. There will be used products at cheaper prices. Click on this link to show Nintendo DSi consoles that are much cheaper than the original retail prices.
Click on the specific Nintendo DSi listing on which you would like to see the contact and purchase details. Click on the "Add to Cart" button to purchase the item.
eBay
Navigate to the eBay.com website and click in the text box. Type in "Nintendo DSi" and click the "Search" button.
Click on the "Systems" link on the left side of the screen and click on the "DSi Original" link. Scroll through the listings to find the Nintendo DSi you would like.
Click on the specific Nintendo DSi listing on which you would like contact details and bidding information. If the item has an option to "Buy It Now," take advantage of it if the price is to your satisfaction.