No two photos are the same, and no two monochrome conversions are the same. But I follow a similar path each time.
Step 1:
Like every starry-eyed Dad, I think daughter is the cutest thing in the world :) This shot is nice in colour, but a bit bland and flat ... I'd like to make a nice black-and-white out of it.

Step 2:
For the best mono conversion possible, it helps to have a nice colour image. So I use Levels to improve the contrast.

Step 3:
I convert it using my action (here). It's nice and clean, but still needs work, of course.

Step 4:
Using Levels, I first add some overall contrast ...

Step 5:
... then some further adjustments in selected areas.

Step 6:
I use Curves to add a little more sparkle to her eyes.

Step 7:
Almost there! Time to add a vignette for emphasis.

Step 8:
Then some sharpening to finish it off.
Roll mouse over to compare original to final:
If you have a question about this method, or any Photoshop question, please visit me at my "Ask Damien" Facebook page.
All content © Damien Symonds 2012