When focusing the microscope one should begin with which objective?

When focusing a microscope, one should begin with the lowest power objective, typically the scanning objective (4x or 10x). This allows for a broader field of view, making it easier to locate the specimen. Once the specimen is in focus at low power, one can then switch to higher power objectives for more detailed observation. Always use the coarse focus knob with low power and switch to fine focus at higher magnifications.