How long is the incubation period between the time someone coughs or sneezes at me and the time i start feeling sick?

Depends on condition: Incubation period for common cold is. 2to3 days but sometimes symptoms can start after 12 hours as it depends on the virus . Same holds true for influenza average is 2 days .Other conditions like Pneumonia etc may have different incubation period . But on average most 2 to 3 days. But symptoms may start earlier at times after 12 hours