Originally Posted by
fillum
Like Rick said, what I generally do these days is preview the built-in presets till I get something close to what I have in mind then "fiddle" with the settings. Some of the presets use desaturation and some use the "B&W" option (I assume that's what you mean by "grayscale").
I think the B&W option gives more control over individual tones but I haven't looked into it in any real depth.
The "Split Tone" settings can give some really cool looks, so give them a try as well.