As a musician—and a brass player in particular—I find myself counting a lot of rests during rehearsals. Not every music publisher is generous in providing detailed cues before a long-awaited entrance. Sometimes you just have to start counting, hoping that you won't miscount and come in too early or too late. If you're like me, you might find yourself thinking like this:
64...65...66...that's a lovely oboe solo...69...70...I wonder what I'll have for lunch...74...75...oh, my entrance is coming up...77...78...we're still in F right?
Many people count in their head or count to 5 or 10 using their fingers. Most of the time this works just fine. The method that I've relied on in countless orchestra rehearsals was taught to me by my high school band director, Greg Hames. It's a way of counting, not just with your fingers, but with the individual segments of your fingers. This allows you to get up to 16 on a single hand.
(Side note: Finger counting differs from culture to culture. Most people in Western countries learn to count in groups of 5 or 10 using their fingers. Counting with the segments of each finger is more common in India and other Southeast Asian countries, sometimes in groups of 12, 16, or 20. Studies have been done showing that the way we count on our fingers has some influence on the way we think about numbers.)
Using your thumb as a pointer, start by pointing to the tip of your index finger. That's measure 1. Move down past one joint to the next segment for measure 2. Continue until you reach your hand (measure 4). Repeat this process on the middle finger (measures 5-8), the ring finger (measures 9-12), and the pinky (measures 13-16). If you have more than sixteen measures of rest, start again at the tip of the index finger at measure 17. I found that it didn't take long for me to know without thinking that one full hand and one finger on the second time through was 20 measures, two full hands was 32 measures, etc. (Advanced tip: try using your other hand to keep track of how many time you have completed a full hand. The first segment is 16, the next is 32, all the way to 256. This is the same idea that abacus is based on.)
What makes this so useful in rehearsals is the fact that four-, eight-, and sixteen-bar phrases are so common in Western music. I've found that the groupings of four segments per finger often line up perfectly with what I'm hearing in the rest of the ensemble.
If you're thinking that it's silly for a 26-year-old to be counting on his fingers, I challenge you to sit through a 3-hour opera rehearsal without once losing focus while you're counting. It's saved me numerous times from missing an entrance. Even if my mind goes somewhere else for a second, I've found that my thumb will keep moving to the next segments, almost unconsciously. There are a lot of ways to count rests out there that different people prefer, but this has always been my go-to method. Ultimately, you want to find something that's easy, reliable, and works for you.