Unscrew the tailpiece knob. Open the tailpiece cover -- if it has one. Carefully unloop the first string from its tailpiece hook or spoke. Unthread the string. Keep the string intact with the banjo at top in its peghead if you are not replacing the string. Unscrew the peghead and fully release the string if you are replacing the string.
Pinch the string at the top end and allow it to hang. Dampen your index finger and thumb with lemon oil. Pinch the string with your lubricated fingers just under your other fingers. Slowly slide your lubricated fingers down the entire length of the string for full lubrication.
Reattach one end of the string the peghead. Pull the string taut and thread it back down into the tailpiece. Reattach the free end of the string to its hook or spoke.
Repeat steps one through three for each additional string. Work one string at a time to maintain proper tension and prevent the need to retune the instrument. Dampen a clean cloth with lemon oil and clean the finger board as well if you are replacing all strings at once and plan on retuning once fresh strings are in place. Change banjo strings for every 30 hours of play.