The Complete Idiot''s Guide to Music Theory

Part 6:
Arranging
242
◆
Each instrument should be clearly marked at the beginning of each staff.
(The first instance typically has the full instrument name spelled out; sub-
sequent staves can use abbreviations.)
◆
In band and orchestral 
scores,
group like instruments together (all the
trumpets together, for example).
◆
For instruments that use the grand staff (both bass and treble clef), group
the two staves by using braces.
◆
Measure lines should be drawn through all the instruments belonging to
the same section—but not through 
all
the instruments in the score.
◆
If you want, you can combine all like instruments on a single staff (all the
trumpet parts on one staff, for example).
◆
If an instrument or voice will be resting for an extended period of time,
you don’t have to include the staff for that instrument or voice during the
rest period.
◆
Use letter markings to notate individual sections of the music. (For ease of
reading, letter markings are typically enclosed in a box or circle.)
◆
Number your measures—or at least the first measure of every line.
(Alternately, you can insert a number mark every 5 or 10 measures.)
It goes without saying that the music you create should also be 
readable. 
If you’re
writing it all out by hand, make sure you produce clear and distinct notes, and
they’re easily distinguishable on the staff. If you have poor penmanship (like I
do!), consider taking a calligraphy course to improve your handwriting, or use a
computerized music notation program to create great-looking music on your
computer printer. (See the “Use the Computer” section later in this chapter.)
These rules apply to the score you compose and that the conductor uses. As for
the music that the musicians themselves read, you have to create individual