If you have a tight schedule and a lengthy presentation or class to give, you can add a little something to the master slide of your presentation to make sure you stay on time. Using the steps outlined below, you will be able to add a small notice (for yourself) to let you know when you need wrap up the current topic and move on to the next slide.
Open the master slide of your presentation and place a small graphic in one of the bottom corners. Right-click on the graphic and select Custom Animation. Add an entrance effect of your choosing. (I find that the Fade effect works very well since it is subtle.) After you have selected an effect, it will appear in the window below. Click on the effect, click on the down arrow next to the effect, then select Timing. Set the start event to With Previous, and then set the Delay. This would be however long you want to give yourself for each slide. (I give myself 2.5 minutes for each slide, so I would set the Delay to 150 seconds.) Click Ok and you're done.
Now that you have this set up, as you are going through the presentation glance up at the screen every so often. When you see the graphic appear, you know its time to move on. Be careful to not go crazy watching the screen or your students will notice and will be distracted. I’ve found that this little trick is extremely useful.
Until next time, remember: When working on something important, it's not possible to hit CTRL-S (Save) too many times.