New plaster keeps curing for weeks after it's applied, and during that time it's sensitive. How the pool is filled, brushed, and balanced in the first month has a big effect on the final color and smoothness of the finish.
The fill should start right after plastering and run without stopping until the pool is full. Stopping partway can leave a visible ring. Once the pool is full, brushing the whole surface once or twice a day for the first couple of weeks helps remove plaster dust before it settles and hardens into the finish.
Water chemistry matters more than usual during startup. Your crew will explain the target levels for your pool; the goal is balanced water that doesn't attack the fresh surface or leave deposits on it. Avoid adding salt, heavy shock treatments, or using automatic cleaners until the finish has had time to cure.
It's tempting to jump in right away, but a little patience pays off. Follow the startup instructions, keep up with brushing, and the new plaster will reward you with a smooth, even finish for years.