Here’s a video I did on how to tune a guitar and the method I use. In the video I mention that I would provide a photo of the current style of tuner and also a link to the site where you can find out more information about these remarkable “gizmos”.
But first…. the video.. 
You will find more information on these guitar tuners at http://www.tuners.com/ I was going to put a photo here on the blog, but you can see what the latest models look like easy enough by going to the site.
Good luck with tuning your guitar and learning guitar chords.
