I usually just add approx 16 Cyan, any where up to 30%Cyan can help, but it will depend on the printers, and the type of project it is for...
Perhaps a little more information on the project would help, such as obviously this is for print, but is it for business cards that will have very small writing on it, and magazine advert - will the text over the black be large and blocky, or will it be small and fine??
How will the project be printed?
If it is an advert, will it ever be used in newspaper print?