Use Pages, the default word processing application for Mac, to design and print labels. Pages 5.5.2, the most recent version of the application as of April 2015, comes pre-packaged with label templates that require minimal editing to print.
If the pre-packaged label selection is too narrow, a selection of free label templates is located on the Avery Label Website. The latest version of Pages is capable of opening Microsoft Word templates, so Mac users are not limited to Pages templates. Word templates do not always render as they should in Pages, but this problem is easily addressed by dragging and dropping elements into their correct positions.
More invested label makers can purchase professional label sets from the Avery site. Creating labels from scratch is time-consuming, but offers more creative freedom. Specify the label dimensions accurately before starting the design process to make sure the final product fits on the designated letterhead. Standard label sizes are located on OnlineLabels.com, where common usages and yields per sheet are listed alongside label dimensions.
Once you have suitable labels, print them on a home inkjet or laser printer. If you want more than a few hundred labels, it is cheaper to submit the design to a professional print shop that offers discounts for wholesale printing.