1) Do not merge down before shrinking image.
2)Keep at 16 bit. If cs5 leave at 16 bit.
3)Do not rasterize layers, especially type layers
4)Do not sharpen image both large and then small. Only when small.
5)Shrink Image, then merge layers.Then copy background layer.
6)Instead of unsharp mask, just use sharpen. reduce copied layer maybe to 75%
7)Create mask. blacken mask. use brush with white about 30%. use brush on areas like skin or anything that is too sharp.
8)Make sure you are using color profile srgb not adobe 1998. If you have to convert it, you will lose some color and contrast. Convert than reajust.
9)If your image is too big, or even if you think it is, create an album at
It will reduce you jpgs and keep the quality better that save for web.