if your purpose is only to show someone how the wireframed version of your model looks like, you could simply take a screenshot by pressing the print screen button if you're on a PC or using Grab (orpressing apple&shift&3) if you're on a Mac.
how to render with wireframes.. I don't know about that one.
R@nSiD (at least i believe it was him) has created a tutorial that leads to a rendered frame with the wireframe on top of the model. you can choose the color of the wireframe, too... but if you don't want a real render, a print screen (and paste into a new photoshop document) will do the trick.