The most important thing to remember when you trace images to create cut lines is to use the highest resolution version of the image possible. Using low-resolution images results in jagged cut lines.
Many images on the Web are low-resolution because that is all you need for display on the Web (72 dpi). An image created for printing should be 300 dpi and scanning images for retouching should be scanned at 600 dpi if possible.
To determine the dpi (dots per inch) of an image:
On a Mac
To see larger versions of the images above, just click on the images.