Very often students will confuse the terms play and practice.  I think of "playing" as going through the music one or several times over.  "Practice" on the other hand has a focus.  This focus includes:

1.  Playing the established warm up (long tones, lip slurs, scales etc)

2.  Playing the music

3.  Identifying the problem spots

4.  Making exercises out of those problem spots

5.  Work from a slow tempo (speed) to the required tempo

6.  Working out the music from small sections to larger sections (i.e. 2 measures at a time, then 2 more measures, the those 4 measures put together)

7.  Playing the piece from beginning to end as a wrap up

8.  Using your "second brain" (the pencil) throughout the process.