When creating a file for print, it is important to consider a few technical details.
This will make your printing experience better and save you money in the end.

Document Layout
If you want your image to extend to the edge of your printed piece, you will need to add Bleed. Bleed is simply extending your image 1/8" beyond the edge of your layout document.
Most document layout applications include a non-printing frame about ¼" around the document, this is a Safety Frame. It's recommended that text not be placed beyond this line, as it may result in an uneven appearance after your printed piece is trimmed.
The edge of your document is also the Trim Line, this is the point your printed piece will be trimmed to.
EXAMPLE OF A DOCUMENT:

RGB v CMYK
All print work should be done in CMYK, not RGB.
CMYK stands for cyan, magenta, yellow, and black, these are the four colors of ink used in the traditional method of printing. The CMYK colors somewhat correspond to primary colors, from which can be mixed colors across the visible spectrum. CMYK is a color mixing system that depends on chemical pigments to achieve desired hues.
RGB is short for red, green, and blue, RGB is a color model used to display color in video systems, computer monitors. Most images taken with digital cameras are saved in the RGB mode. It represents all colors as combinations of red, green and blue light.
The screen image of a picture in RGB will never match the printed image in CMYK. Although these color systems are related, one color cannot directly convert to another.
Converting your images from RGB to CMYK in Photoshop is recommended.
This file has been created and saved in the RGB mode.

This is the same file above, only it has been converted to CMYK so it can be printed, notice the color shift.

Resolution
Carey Digital recommends that all image file formats have a 300 DPI resolution at the final output size. Some imaging software such as PhotoShop, will allow you to increase the resolution of a low resolution image. This will not print correctly, the image will look blurred and jagged.
This is an image saved at 300 and 72 DPI