So, in traditional brass solo literature and etude materials, that pesky lil' ol extra note often shows up before the note you are supposed to play.  Sometimes called an "ornament" and often called a "grace-note"...what the heck is it? (and who is this Grace anyway?) Well, the good folks at the Tuba/Euphonium Association have put together a guide...a primer, if you will (even if you won't) that sets the record straight*.  You can check it out at:

What is This Thing Called Grace Note?

But while you are there...be very, very careful...or you just might learn somethin'!

* Said "primer" is actually a posting of a very hip article by Jeff Cottrell concerning ornaments in general, and focusing on late nineteenth century practice specifically.  For those bibliographiles in the cyber audience, here is the complete article title:

I.H. Odell’s 1899 The Imperial Method for the Cornet:
an Examination in Regard to Ornamentation Practice of Late Nineteenth and Early Twentieth-Century Brass Performance
By Dr. Jeffrey Cottrell, Hardin-Simmons University