  Over the last decade, quasar sample sizes have increased from several
thousand to several hundred thousand, thanks mostly to SDSS imaging and
spectroscopic surveys. LSST, the next-generation optical imaging survey, will
provide hundreds of detections per object for a sample of more than ten million
quasars with redshifts of up to about seven. We briefly review optical quasar
selection techniques, with emphasis on methods based on colors, variability
properties and astrometric behavior.
