How does one tackle difficult guitar song arrangements?
Step 1: Slowly play out all the notes of the music. Don't worry about the rhythm first.
Step 2: Once your fingers are familiar with which notes of the fret board are being used, start to clap out the rhythm of the piece.
Step 3: Combine both the rhythm and notes together and play out the piece.
Step 4: Add in the percussive notes that are indicated in the arrangement. For instance, any string slaps.
Step 5: Add in the dynamics of the piece; i.e. variations of the tone and volume for the purpose of phrasing/interpreting the music infront of you.
AND you're done!