Garage band members need to agree on their goals. If they don't, then some members, inevitably, will be disappointed in the results. If two or three members are thrilled to play at the local bar on Thursday nights but the fourth dreams of one day performing at the Grammy Awards, there will be conflicts. That's why it's important that band members clearly articulate what their hopes are for their garage band. This way, if any members want something different, they can find a new band whose members have the same goals.
Garage bands won't succeed if all members don't share the same level of commitment. If two members meet every Friday night to practice, and the third and fourth members only show up when they don't have anything better to do, conflicts will break out. Garage bands work best when all the members agree to a practice schedule, whether these practices take place twice a week or twice a year. The key is for musicians to play with others who share their same views on the importance, or lack thereof, of regular practice sessions.
Garage band musicians have wildly varying skill levels. This is fine, unless a garage band has musicians whose talent levels are widely disparate. If the guitar player is a candidate for the Rock and Roll Hall of Fame and Museum but the drummer couldn't make it in the high school marching band, tensions might arise. The drummer could grow to resent a guitarist who is constantly outshining all other band members. The guitarist might begin to feel that other band members are holding the band back. Garage bands work best when all their members have the same basic level of musicianship.