I find that one minute at a station is great for beginners because it gives them a chance to feel comfortable with the exercise at a low weight especially if they don’t quite get it right away. 45 seconds is great for a circuit that has a higher intensity. Depending on how you structure your class, your stations can be rep-based or time based. Rep based can be fun for more intermediate participants because it allows the participants to push themselves a bit and try and catch the person ahead of them. BUT, you need to make sure that you have enough equipment to handle at least 4 people at a station at once. You would want to stay away from machines and stick with body weight and equipment you have multiples of. In terms of structure, I find alternating upper, lower, core, cardio works well but if you have a high intensity class, you don’t need cardio as their heart rates are up the entire time!