Correct colour profile for print ready photoshop files

As D. Fosse wrote, work in RGB

Before you convert to CMYK - you need to know more.

Ideally you need to know what print process is being used.

Even more ideally you need the pointer to tell your customer what ICC profile, you should use. 

Otherwise you're trying to chuck a dart to hit a dartboard you can't even see. That’s a significant risk to your reputation.

There ARE good generic CMYK print profiles from ECI, GRACoL etc. and many use those, but you can't guess which one, at the very least you need to know the print process. Coated, uncoated, newsprint, sheetfed, web - it makes a difference.

Note that it's quite unlikely that the SWOP v2 profile you have selected there in color settings will be right. 

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

Until you know the exact printer and paper used, and/or someone supplies you with the profile for that combo, there's nothing more you can do. Profiles "profile/fingerprint" device behavior. 

The customer is unsure of what/which printer she will be using.

By @Gee Aar

Not much to do until you know. Not which printer, but what printing process.

The working spaces in color settings aren't important. What matters is the embedded profile in the file - it will override the  working space.

For now, keep the master file as RGB, in whatever color space it already is. Don't do anything. If it's to be printed on an inkjet printer, it can probably be sent as is.

If this is commercial offset print you're moving into CMYK territory, which is a whole can of worms in itself. In that case it's imperative that you don't do anything until you have full specifications and a CMYK profile that they want you to use.

Come back when you know more -