Different types of microscopes have different procedures to operate it, but here is how you focus a regular light microscope you can find in the laboratory:
1. Adjust the stage. Use the coarse focus knob and lower it to the lowest. This can prevent breaking the lens later on.
2. Clip in the slide. Select the objective lens. It depends how detailed you want to view the slide.
3. Look through the eyepiece. Adjust the amount of light you want by using the condenser. Using the coarse focus knob and adjust to the distance of the stage to where you will see clearest.
4. Use the fine focus knob. Further adjust to the point where the slide can be seen more clearly.
5. When you decide to change the objective lens, make sure you adjust down the stage using the coarse focus knob so that the longer lens won't break!
