I have came up with a melody and some lyrics. Usually I fool around with the guitar and come up with certain tunes just from jamming. I'll jam and when I play something randomt hat I like I'll figure out how to add on to it, elaborate and make it more complex. However every now and then I'll come up with a melody/lyrics in my head and I find it hard to figure it out on the guitar. Any advice?
Hum the tonic note of the tune, and play each note on the guitar to find which one it is. Then think whether the melody is major or minor, and play about within the appropriate scale until you crack it.