My father and his brother and sister performed as the famous Compinsky Trio throughout their lives. My aunt, the pianist, Sara Compinsky was my teacher. When I was nine years old, she asked me to be her page-turner for their concerts, which I did for the rest of their concertizing career. I learned valuable lessons in the process, particularly in the field of sight-reading. Without realizing it at the time, I was developing my sight-reading skills, reading through complex music and fast tempos that I would not have been able to play at that time, but that I could nevertheless keep up with in order to turn the page at just the right time. I learned to look for rhythmic patterns, bass lines, changes in patterns, and the longer melodic lines, and especially counting fromone bar line to the next.
So here is how you can practice sight-reading without practicing: Listen to recordings and read along with the music. Start with pieces that you know or are working on. Then advance to pieces that you don’t know and test your sight-reading skills. Start with slow moving tempos to make sure you are able to stay with the music. Watch the rhythmic patterns and count. Once you can get through the music without losing your place, start watching intervals and sing along with the melody. The most important thing is to keep looking ahead and keep your eyes moving across the staff. This trains you to keep going and not look back. It is one of the most important skills to learn to be able to sight-read while you play.