When focusing a microscope what do you start with?

When focusing a microscope, you should start with the lowest power objective lens, typically the scanning objective (4x or 10x). This allows you to locate the specimen easily and focus without risking damage to the slide. Once the specimen is centered and in focus, you can switch to higher power objectives for more detailed viewing. Always use the coarse focus knob first, followed by the fine focus knob for precise adjustments.