I sometimes have trouble deciding the appropriate tempo of pieces which have no metronome indication. For example, "andante" can mean from 76 ot 109 according to the metronome markings I now have. However, in 6/8 or 3/4 time, does andante generally mean per quarter or eighth note respectively or does it mean per dotted quarter or per dotted half? Before I got this new metronome, I always "erroneously" thought that andante meant around 60. Any thoughts?

Andante means "with movement" or "moving". The right tempo would be one that facilitates a smoothly flowing, but not hastened melody. As far as exact beats per minute, depending a lot on the style of the music, the period and the composer, andante can be anything from <60 to 90>. Words that indicate tempo are highly subjective. The performer uses what knowledge he has about music in general (along with good ol' fashioned intuition) to arrive at a final tempo.

Of course, that depends on what the definition of final is.

Pete