hi one of the most important things to look at in a workflow is your printing sequence, check to see if you are using colour management on or off ( off is a good start) when you send to the printer, make sure you are using the right intent - perceptual or relative colourmetric, (perceptual gives you the best perception of colour), make sure you are using the right paper drivers, make sure PS is working for you and not just in defalut mode on the colour management, but everything is relative as sometimes different printers require different techniques i use both epson and canon printers and the flow is different for both,
Screeb calibration is very important and refer to a previous message that said try and match your screen to your printer,
black and whites can come out like black and whites if your workflow is correct,