Image optimization is an art few have mastered. Useful image editing tools exist that allow images to be edited to reduce their file size while retaining image quality. Using these tools is a good start for optimizing images, but more can be done using advanced tools like Smush.it.
Smush.it uses optimization techniques specific to image format to remove unnecessary bytes from image files. It is a "lossless" tool, which means it optimizes the images without changing their look or visual quality. After Smush.it runs on a web page it reports how many bytes would be saved by optimizing the page's images and provides a downloadable zip file with the minimized image files.