Study the roots and history of southern gospel music. Developing a deep appreciation and understanding of a genre, such as southern gospel music, makes it easier to play with authenticity.
Listen to the classical recordings of southern gospel music. A good place to start is the CD "Southern Gospel's Top 20 of the Century."
Select a few southern gospel songs to learn. Work on several songs at a time. This will keep you from getting bored and you will begin to see various patterns and song structures. Make a list of favorite southern gospel songs such as "This Old House," "What a Savior," "Jesus Is Coming Soon," and "Church In The Wildwood."
Study the fundamentals of music theory and develop your ability to play songs by ear. Songs may be learned by sight reading sheet music or copying the song from a recording. Ear training is an important part of musicianship. Once you develop your ear and know the fundamentals of music theory it will be quite easy to learn songs from a recording. Southern gospel songs tend to use I-IV-V chords changes. The II and III chords are often used as well. For example, in the key of C major the I-IV-V chords are C major, F major, and G major. The II chord is D minor—D major is often substituted— and the III chord is E minor—E major is often substituted.
Two tips can help you to figure out a song by ear. First, listen to the final chord at the end of the song. This will be the key the song is in. Second, listen to the bass notes. The bass plays the root note for the chord. This makes it easier to figure out the chord sequence.
Chart the song out on a piece of paper. Once you figure out the chord progression write down the lyrics with the chord changes over top. Number the chords as well. For example, the chord progression for "Church In the Wildwood" in the key of G is G/G/G/G/D/D/G/G/C/C/G/G/D/D/G/G. The symbols"/ /" signify one measure in 4/4 time. Transpose the progression to numbers and you have I / I / I / I / V / V/ I / I / I / I/ IV / IV/ I / I / V/ V/ I / I. The numbering system allows you to instantly play the song in any key because the chord relationships stay the same. For example, to play this song in the key of B-flat major (Bb) like the Carter family does, the progression would be Bb/Bb/Bb/Bb/F/F/Bb/Bb/ Eb/Eb/Bb/Bb/F/F/Bb/Bb.
Figure out the melody line by ear. The melodies in southern gospel songs are simple as well. Maybelle Carter from the Carter family is a good resource to study. She helped to create the melodic guitar style and the Carter Family included many gospel songs in their repertoire.