NM vs. RM
Grower Champagnes come from small-house vintners who are bringing new taste profiles to the market. On the front label, look for the designation RM (Récoltant-Manipulant), which means that the grapes used are from a single grower. These give more of a return for your money on the quality/value meter.
As far as seeking out a good one, RM Champagnes by Terry Theise are always bangers (his name will be on the back label). NM (Négociant-Manipulant) designates a larger house that purchases grapes from all over the Champagne region. There are more specifics, but that's what Wikipedia is for.