A transient, looking unkempt and destitute, positions himself near the entryway of the supermarket. He hits you up for spare change. Whether motivated by guilt, sympathy or maybe a combination of both, you dig some change out of your pocket and hand it over. We’ve probably all done it. But it’s exactly what we shouldn’t do, said Cpl. Ginny Johnson, homeless liaison officer with the Fullerton Police Department. Johnson was among a group of experts who on Saturday, Feb. 18, gave presentations during Homelessness 101, a three-hour seminar held at Wayfare Fullerton, a shared work and gathering space in downtown’s…