My daughter Mia received a guitar this weekend. It's a kid's guitar, but it's a fully functioning instrument.
I used to play the guitar when I was little (around fifth, sixth grade). I took guitar lessons, and learned how to play some basic chords. First song I ever learned: Bad Moon Rising (G-D-C). I can also hit the notes for Happy Birthday and the main theme to Star Wars. I still remember how to play these songs even though I haven't owned a guitar in several years.
I got my hands on Mia's guitar in the afternoon and tried some of my songs, but the guitar was sorely out of tune. Mia also enjoys playing with the tuning knobs at the end of the guitar, which wasn't a help.
I visited a web site to relearn the basics of tuning. I eventually found Tuner Tool, a free program that let me hear the correct notes for the guitar. But this wasn't enough. I had a hard time matching the notes played by the tuner to the notes played on Mia's guitar.
After more minutes with Google, I found a better program, by Encore. This tool not only played the correct notes, but using a PC microphone (which I had), it "listened" to the notes the guitar was playing, and pointed out whether it was too sharp or too flat. It's quite amazing seeing the display change as the note played. I was able to tune the guitar in minutes! I recommend this tool (and yes, I'll be buying a license).