You find a beaker filled with an unknown clear liquid on your desk, what should you do

If this is to identify the substance, first I would measure its density, then I would attempt to measure the melting and boiling points, and test its solubility in water and ethanol, respectively. I would compare this to a list of known substances that match its basic physical characteristics (i.e., clear liquid) and choose the best match. If you have access to a crime lab and are trained in analytical chemistry, use a spectrometer.