I have seen way to many safety classes be a complete waste of time. The employees just sitting there waiting to leave. This usually is because the instructor doesn't care and is just doing the class because they have to, the instructor doesn't know how to engage, or the company doesn't actually believe in safety and the employees know none of this will actually happen.
To give a good class you must:
1. Believe in the point being made.
2. Make the class as short as possible.
3. Make the point of the class meaningful to your work environment by bringing forth examples from your company or similar work classes.
4. Encourage employee participation. Let them recount a past event, ask how they are supposed to accomplish a given task, or bring up a different point of view.
5. Read the class materials ahead of time, conduct research as needed to make your points meaningful (how many people were injured/killed from operating a lawn mower last year, OSHA posts the statisics online) and be ready to summarize the topic to its key elements.
If you seem like your just reading the materials the class WILL NOT buy in. If you didn't care enough to read the materials they know it's not really important to you. By inference, they know their safety is not really important to you also.
Breaks
For long safety classes make sure you take breaks at least once an hour. Unless your very entertaining it's hard to hold their full attention for longer periods. Also, physical discomfort, especially in cheap seating, will distract from the learning experience. At the beginning of a class I will state that they can learn just as well standing as sitting and if anyone needs to get up and stretch during class it's ok.
One thing I like to do in a Safety Class is to keep the students engaged. When I had a longer class where students would get breaks I would always say "go get a drink, go to the bathroom, stretch, check your messages, or just get some blood moving."
But many students just sit there so I would put up a slide show during the break with pictures of mildly humorous safety issues for the students to consider and discuss. Feel free to use it.
Change it up
Avoid having the same style of class every time. It gets boring. You can:
1. Add in a quiz. A quiz tests their attention and knowledge.
2. Show a video.
3. Have an employee give the class. Make sure you give them the materials ahead of time and go over it with them beforehand to assure they have a handle on the material.
4. Separate the students into teams for a quiz competition with a minor reward. This is great for a recurring topic each year as the students have heard the material before. You don't even go over the material beforehand. Just go straight to the quiz and teach as necessary after each question.
There are lots of fun premade quiz formats. Try typing in "Jeopardy Game Template" or "word search maker" into a search engine for example.
5. Walk the class through the work area showing the tools to be used, the ppe to be worn, the location of eye washes, emergency exits, or any other point of note.
6. Do hands on demonstrations.
Below are some sample thoughts/classes for you to consider. I've got a bunch more and may eventually put them online. If you are looking for something send me an email.
Heat Stress
One of the most important subjects you can train staff on is Heat Stress. It's a lesson that applies both at work and at home.
Supervisors
When a new supervisor is hired either they were a line employee and really don't know ALL the things a supervisor is responsible for or they are from outside the company with previous experience but who knows what that other company told their supervisors to do. That's why we always give newly hired supervisors an orientation class with regards to safety. Many will have no idea of the non-production role they have. Here's an example of a slide show I used to use. You would want to customize it and use your companies style.
Fire Extinguishers
Besides your company safety programs the 2 classes I'd recommend for everyone are First Aid/CPR/AED and Fire Extinguisher. A trained Fire Extinguisher user can save your whole buisness and the lives in it. The Fire Extinguishers are already mounted on the wall around your buisness but it might be for nothing if you don't do a little training.
Here's a slide show I used to go along with the hands on training.
Tools
Most employees use some kind of tool to do work. Also most employees will take short cuts that put themselves and their work at risk. For every tool they use they should get some training. It could be very short. It could just be a sign off sheet where their supervisor goes over each item to be used. (for more complex tools more is needed) But if they ever get hurt and you haven't done training on that tool, you could be at risk for a citation and, more expensively, a lawsuit.
Here's a slide show with some baseline training on Hand Tools I used to use.