I worked in the autoparts retail sales area for a few years. I've seen random 'ticks' come mostly from the accessory drive of the car (read belt, pullys and anything they connect to). Typically its a bad bearing, they don't always produce a squeal, sometimes they do tick. Other times it is internal to the engine, a lifter, rod, even a PCV valve with a leak.
Without hearing the sound, and moving around the engine compartment to hear where it is louder or softer, and without knowing what kind of car it is; it will be impossible for us to pinpoint the culprit.