What's the right way to prepare graysclale images to print in photoshop?

@Jul B @D Fosse writes:"Under working gray, click "load gray". Then navigate to the appropriate CMYK profile that you will use for printing."

'appropriate CMYK'  is a very important phrase here.

@Stephen Marsh writes: "you should use the correct ICC profile that describes the intended print condition! Perhaps your print service provider can recommend what target condition to aim for."

so,  the: "appropriate" profile that @D Fosse mentioned is "the correct ICC profile that describes the intended print condition" as described by @Stephen Marsh

Its all about the print condition. 

That ICC profile will tell Photoshop what dot gain* to expect, i.e., what values to use to ensure your file values are printed with an appearance that reflects those intended values, 20% = 10%, 30% = 30% etc. If the press dotgain is not correctly accounted for then your greyscale will not print as expected. 

*(dot gain is tonal increase due to the spreading of ink on paper making the printed material appear darker than intended)

I hope this helps neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right' google me "neil barstow colourmanagement" for lots of free articles on colour management Help others by clicking "Correct Answer" if the question is answered. Found the answer elsewhere? Share it here. "Upvote" is for useful posts.

Here's how you do it:

Under working gray, click "load gray". Then navigate to the appropriate CMYK profile that you will use for printing.

It will look like this in Color Settings:

When you've done this, "Black Ink <CMYK", will appear as a regular option in Convert to Profile and Assign Profile. If you already have grayscale documents, you can now convert them to this, or you can create new documents.

These will print on the black plate only, and match what you see on screen in Photoshop.