What songs should I practice beforehand?

There are no specific songs to practice. Practice some good ones you like, that others might enjoy playing too. Advance emailed class materials include a mini-songbook with some good choices. You’ll want to practice a few to do in a small group setting. Know the chords and practice the song (in-tune singing not required) with the words in front of you. Try after a while to not need to read the words. Most of the songs in the class will probably be new to you, so the skill in play will be: “learn new songs more quickly”.