Hey all,
I'm a new member with a few years of commercial retouching experience, will try to help out with others problems. Have got a fairly urgent one myself...

I've got a client who gets their images supplied in RGB (since the files are being published in a variety of publications) however, the resulting prints i've seen so far are very muddy, especially compared to prints from other photographers who i'm sure are also providing them in RGB. my monitor's calibrated, and i'm giving them the right RGB colour space. i know there's no exact control i can have over this, since i'm working in rgb, however, i was wondering if anyone knew about some general guide perhaps, something in the RGB values i should be looking at that might help me out.

mac ;)

Can you post an example to narrow the problem down a bit?

sounds like a problem with the ICM...contact the printer and ask them to send you theirs...then you should be able to convert it to CMYK with that ICM and get resonably good results

The RGB colorspace is much larger than the CMYK space, so there will be losses in that direction if you don't take that into consideration. Try softproofing in CMYK, or even working in CMYK mode (there's very little loss going from CMYK to RGB).