First thing I ever worked out for myself was the magic roundabout theme on one string when I was 8 (didnt know how to tune the others yet) ,then it would have been the Thames TV link music, the bit where the mirror image of bits of london stuck together appeared. Had been shown how to tune by then, and the tune was D,G,B,G,C,B,G,D. If you're old enough (and lived in london) you'll remember it. First proper riff would either be ghost riders in the sky or apache. House of the rising sun and layla where the other memorable ones between 8 and 10yrs old. My memory of things thirty odd years ago aint as good as it could be :)