I'll try to answer some questions as specifically as I can to help some people on here get a more detailed idea of what goes into a class,
It all rotates around what goals you have for your class. Try to keep things related and relevant, so they consistently support your class purpose. For example, say you want to really focus in on precisions in today's class, since they are all very weak in that area:
Your class might start with a warm up that involves a lot of motion of the lower body. Jump-rope type movements that get the ankles flexing, and the calves, shins, quads, hamstrings, glutes and hip rotators going. Once you feel that the heart-rate has been high for a long enough time, and you feel as though each primary area of the lower body has been hit and is properly warmed up for their safety, that's when you can move on.
After that, I might do some joint rotations. If you're planning on doing some jumps and dynamic, medium impact movements, you'll want to warm up their joints. Really, you should do joint rotations every class. But focus on the area you're utilizing in the class the most. Maybe do a few extra motions for the ankles and knees.
It's either here, or later on that I'd elect to do conditioning, if that's a regular part of your class. Focus on building the appropriate skills that link with the theme of the class. In our example, we're working on precisions, so my initial reaction might be to focus on building explosive power in the legs, by doing movements like box jumps, burpees, and those kinds of dynamic motions. In between, I'd do some ankle conditioning, and maybe some resistance strength training for certain areas, like hamstrings or glutes. It's not a bad idea to do conditioning for the other parts of the body, just make sure you have a goal and a purpose that points your conditioning in a certain direction. As for -how much- conditioning, that's a common problem. My solution is simple. Do the workouts with them, feel it, and carefully observe them as they go. Compare how you're feeling to how they look, and find some middle ground. Be prepared to push them a little, don't be afraid to make them go through a little agony. Most of your students are there to be pushed. But you also need to give them something they can chew, or else they'll realize they can't fulfill what you ask of them, and become demotivated. Judge it by the class, by the person, by the minute.
After that, you might pick and choose the order. Here, you could go straight into the technique training, especially if you have a lot to cover. Or, you could stretch. Whether you want to do stretching as it's own specific activity in order to build flexibility, or whether you're doing stretching as a reaction to a day of training will be one of the factors that help you decide when (and if) you want to do some serious stretching that day. Also, what level of warm up you did will dictate what you do. If it's a light warmup, stretching won't be as effective until later in the class.
So then you can move into your technique, which is completely up to you. Use your methods or progressions or whatever you feel is best to teach them the technique. Make sure not to overload them with information at first. Give them what they can digest at once, and give them enough time to digest each step, or they'll feel left behind and demotivated.
Now you should be well-past the half-way point of your class, and they've had a sufficient workout, and learned a good amount. Enough to be content. You should put the main content of your class (which in the case of my classes, are conditioning and technique) in the first two thirds of your class, and let the rest fill in. Things like discussion of philosophy and history, learning information on physics and anatomy and nutrition, warming up, warming down, stretching, team-building exercises, games, all those kinds of things I use as tools to fill the gaps. Sometimes they get lots of focus, sometimes they don't, depending on how it relates to the theme or purpose of that particular class. Again, it's about stringing everything together so that it's relevant and coherent. You will impress your students when they realize at the end of the day everything you did was targeted towards developing something specific. It'll give them confidence in your ability to lead them through their goals.
Ending the session is often up to you. Obviously, a warm down is suggested. Some light stretching, maybe some deep breathing, some meditation if you have knowledge on that subject, things that help them transition from that training zone back into the real world, both physically and mentally. Also, remember that their bodies are nice and elastic at this point, so long as you haven't taken too many breaks. If you want, the end of the session is the time to bust that ab workout that sends everyone home sore, or to do that one final challenge that makes everyone go home feeling accomplished, or motivated to succeed next class.
Above all, keep it positive and joyful. Your students are looking for a good learning environment, somewhere they can truly feel separate from their daily toils and struggles and can find refuge. Be sure to provide an environment that they feel comfortable and happy in. That is what will keep them coming back, above all.
Just my thoughts on some of the questions in this topic. I tried to be as vague as I could to allow for your ideas to be placed in, while being specific enough to be helpful. I hope it helps in some way! Let me know if you have questions, I'm more than happy to explain things.