By simple definition, A chorister is a member of a choir.

A good chorister therefore entails, not just being a member, but a dedicated member of the choir. many choristers are just bearing the name and they do not know what it means to be a good chorister.
One thing is that, its not just about the choir, in any organization one belongs to, the one should not behave as though, the one was forced into it( that is if you were not forced into it). You have to be really committed to any association you willfully joined.
There is nothing that kills any association like non-serious members. You cannot say you are a chorister and you do not go for choir practice. Not just going for rehearsals on Saturday, but going for weekly choir practice.
It kills the spirit of any choir master or music coordinator whenever he/she perceives that his/her efforts are in vain.
Besides that you can never grow if you do not improve yourself. If you keep thinking that you are the best and that no other member of your choir sings better than you, that is the beginning of your failure as a chorister.

In all, to be a good chorister or even a good singer, we need to go for weekly practices and voice training. We need to encourage whoever is teaching us, whether choir master, choir mistress, music director or any other person.