Watch the Slide Positioning and Intonation online guitar lesson by Andy Aledort from Slide Guitar Power
Slide positioning and intonation - playing notes that sound in tune - are essential for proper slide guitar playing. For a note to be intonated properly, the slide must be positioned directly above the fretwire, and try to keep the slide (somewhat) parallel with the fretwire. Apply only enough pressure to sound a note clearly; do not allow the slide to bang into the frets. Also, lightly rest additional fret-hand fingers across the strings behind the slide, as this will eliminate unwanted overtones and ghost notes.