Sometimes, when a page of score can’t be reduced into divided systems, it’s good to leave some blank staves alerting the conductor to instruments about to make an entrance. Also, leave blank staves on a page if the instruments are going in and out of being used every 2 to 3 pages. This way, the conductor can slot the instruments into his vision as he turns the page, instead of hunting for the abbreviation on the left side.

Scores - Blank Staves