If you are creating a multi-coloured document it is important that you create your colours using the CMYK pallets in your design program. Note: MS Office Programs are not capable of producing CMYK output.
Working with CMYK pallets will give you true colour output when printing.
Prepare your artwork with appropriate sized images and logos, e.g. if you have an A4 brochure to be printed, when creating the artwork re-size your images proportionally before importing into your document. Resize it to the size you want in Photoshop or another program before importing into your document. It is important to keep your files at a manageable size while retaining print quality. If you want a spot colour offset printed job then choose whatever Pantone PMS colours are required.