How to give a good lab tour?
Depending on your data and work, it maybe beneficial to make some sort of visual representation and/or simulations of your work. People are draw to visual representations that move and do something. Stationary images, while informative, are not always interesting to the layperson (or well even those interested in the field). You could create a presentation that shows the hardware that collects your data, the raw data and then create a road map back to your students at your lab. Show screen grabs of any software that your students might utilize from day to day. You don't need to get too elaborate and there are many resources (power point, desktop applications, web applications, etc) that you could utilize to create your presentation with whatever level of effort you wish to put into it. 

I would also suggest looking for someone to consult with, not affiliated with your lab, to view your presentation.This way you can get a fresh outlook on how your presentation flows. If your school has a scientific and technical (STC) writing program, I would also suggest you talk with someone in the program about your presentation. They might be willing to help out with making things more interesting and clearer for prospective visitors. You could possibly even see if a student in the program would be willing to create a presentation for you as a senior project.