this is a rough out line for a western style mohair cinch, the pictures are of my first cinch that I was testing tecneques on.
this is what I came up with from my reserch. It is by no means perfict but my hope is to clarify some things for you.

materials:
2 Stainless steel, or brass buckles
70' of 8 ply mohair cording. (for a 19 strand cinch)
2 ply mohair cord (langth depends on decoration)
A flat serface
patence, and time

Step 1: Starting

first attach your 8 ply mohair cording to a stainless steel or brass buckle by thereading your cord though the first buckle (without knotting it), as you thead it through the second measure the distance between them making sure you keep the same distance each time you go back and forth. if you have a double bar follow the picture diagram for lacing it though both bars securely.

Step 2: Tight

once you have all of the strands though make sure they are even! if not pull on both sides at the same time gently, remember we havent secured it yet.
make sure you have exra (about 2') for finishing off on either side.

Step 3: Finishing Ends

to finish off the ends we will be doing a weaving pattern, to show this I used a brown cord.
You have to start with the bottom outside cord that is beside the excess we resurved first, or the first one if you don't have two bars. if your outside cord is on top of the excess flip it over.

take the excess and go up and around the bottom out side cord, pull downward and repeat, go all the way across and revere going the other way.

for detailed instructions for this and other methods have a look here!

Step 4: Decoration

these pictures show how to add a bar in the center.

use 2 ply cord for this part.

you start with a X on one end of the Cinch.
next go over and under alternating strands each time.

here is Pop Wagner explaning this step is detail.

Step 5:

same as step 4 only reversed.

I find it helpful to bundle the ends that i'm working with,

Step 6:

to finish off any ends, use a crochet hook to pull the cording through the weaving and trim.

the main thing to keep in mind is thightness, you don't want anything loose.