I started down the road of becoming a high school science teacher, but when I couldn't land a teaching gig my first year out of college I had to look for something else. That's when I wandered into technical training and starting learning how to teach adults.
I can't claim to be a "great" technical trainer, but I have learned from many greats along the way. Here's a hint on how to teach adults well:
Think like a cook.
Everyone knows that there are really just some basics in the way of food and water that are needed to survive. But you don't want to think like a survivalist, you want to think like a gourmet chef. How do I make this food unforgettable? You need the core component (for example, meat), the adjacent supports (for example, potatoes), and the spices (for example, salt and pepper).
So what are these things in training?
The Core Component: Know the subject that you are teaching. I know it seems obvious, but students can tell if you are skimming over the surface of something where you have no depth of knowledge. Become a confident expert! If I'm teaching about DNS servers, I need to really understand the moving parts of DNS, how it works (when it works) and how it breaks (when it breaks). What are the different flavors of servants and clients? How has it changed since 1983? So as an instructor you need to make sure you are prepared. This includes also ensuring that if you are going to demonstrate tools, you have the tool properly setup for your presentation. Students don't want to watch their instructor searching documentation mid-class. Be prepared!
The Adjacent Supports: Know the ancillaries to your subject. For example in the world of DNS, what does the security guy worry about with regard to DNS? How about the Active Directory administrator? How does DNS interface with other protocols like DHCP?
The Spices: Make your instruction "taste" good! This is where we really separate experts from expert trainers. Manage your classroom with confidence and create an atmosphere that is comfortable for learning (which means both asking and answering questions on the student's part). Provide motivation so students know why they need to learn something. Change up your presentation methods from lecture to jokes to demo to stories to Q&A. Ask for feedback, ask for clarification. Used both closed and open questions depending on what you are trying to teach. Learn multiple analogies for different situations or to help a student understand. Draw recognizable pictures and write legibly on a whiteboard (physical or in software). Modulate your voice so that students can pick up on your meaning.
A few last cooking tips: If I order a multi-course meal I expect it to start with small plates that build up to the main course and finish with a dessert. Your teaching should do the same. Learn to organize the information that you present in such a way that it makes sense and builds on previous knowledge in incremental steps. Provide distinct breakpoints for the mental palate to be refreshed. And don't be afraid to ask for feedback. A good chef knows that the feedback from the customer is critical to keeping the restaurant open. As a trainer, you need to accept criticism and find the next thing to work on to make your next presentation even better.