Grace notes augment the note just after them. The way I play them is I rehearse them a few different ways between rehearsals and listen to what the music is trying to tell me in the emotional sense. See, most people read grace notes and they add them as if they were a clipped sixteenth ahead of the "straight" note. But what happens more often than not is you sort of get an overplayed grace note tied to the next note. It doesn't sound right.
Gary is giving great advice here. There are alot of great points on this thread. When you listen to how a grace note properly augments the note just after it you hear more than just two notes albeit with one sounding "clipped". You're really listening for the emotion, the soul the musician is putting into the phrase. Because it isn't about how fast or how technical something is, (borrowing from two very interesting threads on here recently), it's really about the dynamics of each note.
This ties in so well with the thread on hearing and technical ability it's almost scary lol. Because you see the technicality of a grace note on a page. And you might even play them with a rudimentary understanding. But then you hear someone who uses grace notes in the same fashion the great authors of the world create their dynamic paradoxes with simple prose. Now you know what to listen for in determining how closely your technique matches what you know should come from your horn.
Harv