Scanning prints is always a problem. Scanning negs can be a problem for B&W, but works really well for normal c41 film.
For Colour:
I scan at approximately 2 to 4x the final res. CC (I use the curve tool opposed to the cc or variations tool -- less crossover) spot at 100 to 200% and then resize in 3 to 4 steps. If the image is 2000 pixels and I need it to be 500 pixels I will do the following:
1. Resize 2000 down to ~1400, unsharp mask 30 to 40%, 2-3 pixels and 1-5 levels
2 Resize 1400 down to ~ 1000, unsharp mask 30% 1.5 -2 pixels, and 3-7 levels
3 Resize 1000 down to ~ 700, usm 25 - 30% 1-1.5 pixels, and 7-10 levels
4 Resize 700 down to 500, usm 25% 1 pixels, and 10-15 levels
This slow resizing with adjustments in %, pixels and levels gives a more realistic sharpening w/o the halo. Adjust the %, pixels and levels to taste. It is important to do it as you resize and to resize as in steps so that the details survive the lose of pixels.
I also record the whole thing as an action so that i don't have to keep tweaking the USM, and image size settings. The key is to scan everything at the same size. Most scanners are at their best at full resolution -- this may seem obvious. It is far better for you to decide what pixels get thrown out than the scanner.
For B&W use the curve tool to adjust density and contrast and the eyedroppers for black and white points. Don't use auto or the lightness and contrast tool! Also the auto settings on PS are set to .5 for both black and white points I reset and recommend a default of .1.
FWIW I have used this technique on images that have appeared on the websites of GM, Ford, Vistion, Allied Signal, Continental, Compaq, and many other corp websites.