These beers are probably most similar to Saisons.  They tend to be earthy with a little malt sweetness and medium hop bitterness.  The hops used tend to be of the Noble variety.  Bière de Garde beers are usually cellared and bottle conditioned.  The presence of ethanol is usually evident.   Color-wise they run the gamut from golden yellow to light brown.  Alcohol content generally between 6 - 8%.