If your job is to be printed CMYK work only in CMYK. Convert all bitmaps and imported graphics to CMYK. Choose colours
exclusively from a CMYK palette.
If your job is to be printed in spot colour work exclusively in Pantone colour. All bitmaps and imported graphics must separate
successfully onto your chosen spot plates. Choose colours exclusively from a single Pantone palette, either Pantone Coated or Pantone Uncoated.
Don't expect what you see on an uncalibrated monitor to be a colour match for your printed job.
Don't expect what you print from an uncalibrated printer to be a colour match for your printed job.
Don't expect CMYK to be able to reproduce pantone colours.
If you are working in a program that is natively RGB, eg MsPublisher and MsWord, then you do not have control of colour.
To make colour judgements you should calibrate your monitor or printer to simulate low gain litho print and/or invest in a suitable swatch book.