Hi Alden, imo a new member has to be spiritually sound and doctrinally right. Besides that I hope and pray that he or she has the chops and strives for excellence. An initial meeting for coffee or lunch breaks the ice and you get to know more about him or her. Then an invitation to a rehearsal lets him or her see what the worship team is all about. Maybe you let him or her sing or play a song during one of your rehearsals. And finally you invite him or her to practice for the "real thing" and play one Sunday with you and see how that goes.