This guide is a simple method I've been using for many years that is great for small home gardens. This method scales well but might be better off adapted to cloning plug machines for very large scale production. The basic methodology is the same.
You will need a few things to get started. I like to use a cheap peat based germination mix with good drainage and water retention, a good cloning gel, a clean sterilized sharp blade, and some plastic cups.
I use a bleach solution of 30% or more and a torch on the blade as well. The effort to keep sterile is to prevent contamination that could interfere with the cloning, and to prevent the spread of viriods and disease. If you re use any containers, trays or blades they need to be well cleaned.
Take your clean plastic cups and cut the top rim off half of them, the other half make drain homes in the bottom.
Gather your cuttings. They should be about 3-5 inches long and preferably have at least one node on the stem. I clean them with a solution of 30% bleach, then rinse them off and place in a cup with fresh water.
Fill up the cups and I moisten the media with boiling water. This sterilizes the planting media. Poke holes and let cool to room temperature.
I clean up cuttings and the nodes and make a angled cut at the bottom of the stem as pictured, then dip the cutting to the depth of planting in rooting gel. Place the cutting in the cups and water them in. I use a very mild organic fertilized water ph'ed to 6.5-7 or so (0-1-1 NPK 1ml per half gallon).