Figure #1: This picture shows the various parts of the hoof on the bottom of the foot.
A) identifies the heel regions of the foot.
B) shows the toe region on a claw that has not been trimmed.
C) identifies the outside hoof wall, and
D) indicates fresh sole after being trimmed.
Figure #2: Often the first place to start is the dewclaws. The tips of the dewclaws should be removed. These structures will bleed if cut too short, so it is important to remove small amounts on a frequent basis.
Figure #3: This shows the bottom of a foot that is in desperate need of a trim. Notice how hoof wall has over-grown between the two claws allowing dirt and potential infection to be trapped in the interdigital cleft (identified by the white arrows).
Figure #4: The goal of trimming the foot should be to get the bottom of the foot to match the angle of the coronary band (identified by the white line). In this picture, the excess toe is being removed to a level where the bottom of the foot will be parallel to the coronary band. The intended bottom of the foot is indicated by the black line. Notice how the white and the black line will be parallel once the foot is properly trimmed.
Figure #5: This picture compares the untrimmed claw on the left to a trimmed claw on the right. Notice how much shorter the toe region on the trimmed side is in comparison to the untrimmed side.
Figure #6: This is a picture of a fully trimmed foot. The bottom of the foot has also been leveled with a plane.
Trimming hooves took me a couple times before I got comfortable that I wasn't going to make the sheep and pigs bleed all over.  Here is the information I used to get me started, I had never trimmed a hoof before we got the sheep.  This will be a regular (read; monthly) chore for the sheep, and every few months for the pigs and goats.  This step-by-step learning tool was borrowed from the infovets.com website.  * When learning how to trim feet, begin by removing small amounts of hoof wall at a time. Go slow and take the time necessary to let the foot down and check the balance of the foot. Removing small amounts and taking time to check balance on the foot will help reduce the chances of over-trimming and entering the sensitive structures of the foot.
During a hoof trimming session with the sheep in 2010, 2 of our nieces were over for a weekend at the farm.  Then 10 years old and 7 years old, the girls found it most interesting.  They even collected the hoof cuttings in "treasure bags" and took them home to the city.  Their momma (my sister) was not as excited about their "treasures" as they were, and a new rule was established at their home;  No hoof trimmings allowed in the house!