Tip 1 - Use the correct dpi web images should not exceed 72dpi and should not be used for print and printed images should be at 300dpi at the size they intend to be printed.
Tip 2 - Screen images
The image you see on screen will vary from the printed one because all monitors are RGB and most prints are CMYK. These two colour modes cannot produce all the same colours.
Tip 3 - Check your file types
If you intend to supply artwork to any printer or design always check the file types that they will accept before creating artwork
Tip4 - Expect variation
The design & print process is a complicated one and although every effort is made to reproduce documents correctly variations of upto 10% can occur in all areas such as colour, size or quantity