Blair Graphics makes the following recommendations for successful color printing:

Resolution
Any raster image needs to be 200dpi at full size to print properly. Any higher resolution will increase file size as well as RIP (Raster Image Processing) time.

Raster images are pixelated for continuous tone.
Vector images are not pixelated at any depth and produce crisp, clean lines for type setting.

Fonts
Be sure to send your font files with your document files, or convert all fonts to outlines, this will minimize rejustification problems during output.