what are the best settings for prints?

I was wondering what the best settings are for prints.

Example If I were to use Mpix for my prints what would be the best file type to send them? If I were to do them at home?

Im wondering because I have never really had to do my own prints but if I start doing more pictures for people and they want to order their prints through a printing place that I use, do I give them company a different file than a JPG file that I would give to the client?

Thanks

In general, you'll need a 300 ppi JPG image for the print size you want printed. For example, a 5x7 print would be sized at 1500x2100. Also, you should sharpen MORE for a print than something you would view on-screen.

Calibrate your screen, use colormanaged software.
Call them (or check the website)
Unless they specifically tell you otherwise, send an sRGB jpg.
Sharpening depends on whether or not they sharpen. If they don't, Dave's sharpening advise is a good one.