Ahhhh! This, my friend, is the role of Imageready (Photoshop has fewer options). My advice is to follow this list:
- Find and remove all meta tags. If your image is small (i.e. part of an interface), the weight of many images containing duplicate metas can add significant size to the overall project!
- Look at the optimized preview, set the bottom stat to 'Optimized/Original file size' to track your size reduction, and then look at the optimize palette. Adjust the quality settings of your chosen file format until you get a good mix of filesize and overall image quality.
- Stick to JPG or GIF formats. PNG is a fantastic format, but it has limited browser compatability, and its filesizes are usually enormous.
- Be aware that JPGs usually compress complex images better, but can leave an overall jittering that may look unsightly in images with large amounts of flat color (i.e. certain interfaces). In that case you'll want to stick with GIF and just reduce the color density until the difference in the optimized version is perceptible to your eyes.
- When you are done, click on 'Save Optimized' to save your newly optimized image.
Hmmmm... this kind of advice is actually most ideally suited for a tutorial! I'll add it to my 'tutorial ideas' list and get around to it soon. In the meantime I sure hope that my advice helps!
