Starting on a good footing: Shearing school
The number one piece of advice I give all potential shearers when deciding to embark on learning this skill is to get proper lessons. There is just no substitute for learning from a qualified pro. Youtube videos and articles like the ones found on this site can be very helpful, but having an expert standing over you, literally guiding your hand, showing you all the pitfalls, can save you hours of frustration and perhaps avoid seriously hurting your animals.
There are many shearing classes available out there. There are even a few shearers that will offer one-on-one training for the right price. I don't have experience with all of the classes and instructors that currently offer lessons, but I do have some opinions.
First, I would avoid taking a class from another farmer/shearer. Someone who shears maybe 100-200 animals a year on their own farm. They may be great, but until you do this full-time and professionally, you're just not going to learn the most efficient way of doing things, and those bad habits are going to be passed onto you.
Seek the best, most qualified professionals in the industry. Watch their videos. If they are not shearing an animals in under 6-7 minutes, then they are not operating at peak efficiency. This will translate into bad habits for you that could potentially add way more than a few minutes an animal to your shearing routine. That time matters. It's harder on you, harder on the equipment, and harder on the animal. An extra few minutes on the floor, bent over, with clippers in hand, can really wear you out. It's when you're tired that mistakes happen, and mistakes in shearing usually involve blood. That additional time on the ground is also stressful and tiring for the animal. A heavily pregnant female will be fine getting sheared for less than 10 minutes, but 20-30 minutes is entering the danger zone for stress. Keep that in mind when looking for the person to train you.
Finally, make sure that you are getting a good bang for your buck. I'd recommend a two day class (although those seem to be less common nowadays). Ask how many alpacas you'll actually be shearing. If it's only one, that might not be enough to prepare you for the real deal solo. Ask how many others will be participating. If there are 15+ people in the class, you're not going to be getting that much one-on-one time with the instructor. It's all about getting the most practical experience you can.