If you want to learn to frame, start by taking classes, and consider education to be an ongoing process. Just as it is in the photo industry, technology in custom framing is always changing.
These tips assume you are framing an inkjet print:
Wear gloves and use a sneeze guard!
Any tiny droplet of moisture can damage a digital print. There are many other considerations to framing digital output beyond protecting it from the ravages of things like adhesives or saliva. For instance, a mounting press set to the old standard of 225 degrees Fahrenheit will wreak havoc on an inkjet print, as inkjet inks typically boil at 156 degrees Fahrenheit.
Additionally, inkjet prints on canvas that have not been stretched may crack around the edges.
Be sure to use acid – free materials and spray your prints with a coating to protect against damage from moisture.
Also consider protecting your images with conservation glass. It will cut down on the reflections that contain harmful UV light.
This is just a starting point – those of you with actual framing experience, feel free to jump in and add to the list in the comments file.