If you're selling items on Craigslist, boost the effectiveness of your advertisement by including a photograph of the item. A picture lets potential buyers know the visual condition of the item, the approximate size and details -- such as color and patterns -- that may be difficult to describe. Before adding a picture to a Craigslist ad, resize the photo so it will upload quickly during the ad creation process and when potential buyers view the ad. Since viewers see the picture on a computer monitor, and not in print, use photo editing software to reduce the photo's resolution.
Open a photo editing software program on your computer.
Select the "File" and "Open" options from the program menus. Choose the digital photo to resize for the ad.
Choose the "Crop" tool. Type new image dimensions -- such as 4-by-6 inches for a vertical picture or 6-by-4 inches for a horizontal photo -- into the image size box.
Change the dpi -- or dots per inch -- setting to 72, the maximum resolution output by standard non-high definition computer monitors.
Click and hold the mouse down to drag the crop tool over the image to trim off any excess background and make the item for sale look larger. Release the mouse button and double-click to make the crop.
Save the new, smaller image file with a new file name so you don't overwrite your original file.
You can include up to four photos per advertisement in the housing, for sale or personal ads sections on Craigslist.
If your photos take too long to load, further reduce the image dimensions of your photo.