And what are the associated risks?
For most people, having a shop do the mount is a hassle-free and relatively inexpensive way to mount bindings. Shops will often mount the ski "on the line" but many will mount it to your basic specifications.
Why mount yourself?
In my experience, the main reason someone would choose to mount their own ski bindings is that they want to mount older but still serviceable bindings that a shop refuses to deal with, they want to do a custom mount involving binding inserts, swap plates, quiver killers, or they want to use multiple boots and mount the binding in a way that multiple BSLs (boot sole lengths) would fit, which would not work in a standard mount.
Tools & Templates
A binding mount can usually be done with some C-clamps, epoxy, masking tape, a power drill, some bits, and a binding template. It is difficult to provide templates here as they are usually printable in PDF form and specific to the binding make and model. They are available online from sites such as: Binding Freedom, or Slide Wright both of which I've used in the past. An important thing with templates is to ensure they are printed to scale.
As the comments above mentioned, mounting skis is a somewhat precise process, which definitely embodies the adage "measure twice, cut once". Common risks are: drilling too many holes and turning your skis into "Swiss cheese" thus making them very fragile, drilling through the ski if you aren't careful, or incorrectly measuring by enough of a margin so that you can't click in.
General tutorials are available online, in fact my friend and I have written several from our first few mounting experiences. I'll try to summarize the steps very briefly here. Extensive tutorials including video can be found at: Binding Freedom Tutorials, Teton Gravity Forums, Wild Snow articles, or articles here, here, and here.
Acquire the following: power drill, printed template, epoxy, a sharpie, drill bits slightly smaller than the binding screws (~3.6 mm), a pilot hole bit, a ruler, C-clamps, and a sturdy table.
Clamp the ski to the table. Find the center of the ski "on the line", the line printed on the ski from the factory.
Align the binding template, centered on the center point, and tape it down. Measure a lot.
Optional: Visually check by placing bindings over template and putting the boot in. Center-punch the template hole marks to ensure the bit won't skip on the ski's surface.
Once you are sure on the placement, tape a "stopper" around your drill bit(s) at about 9mm (standard wood screw thread length). Drill some holes.
Once holes are drilled, put a small amount of epoxy on each screw and screw bindings in.