The growth of plants, the climate and weather, and events in history that correlate to past world transits... all this showed me that the ancients were right.
As for personal transits, years ago I once had a client come to me who said that he lost his keys while swimming at the beach. I asked him when this happened, where he went, and who was with him. I run time cycle charts on these dates against his own transits. I saw positions in his own personal transits relative to the present geographical transits that indicated that his keys were stolen from him by a person he knew.
I will not go into detail here about how I knew this because it is quite advanced, but the method is one that has been around for a long time and is known by experienced astrologers.
I triangulated his transits into the near future, running them into the days and weeks relative to his geographical position and told him that the person he knew would attempt to enter his apartment at a specific time and date when he thought his friend was not home.
Because he was scared, I helped him out by changing the geographic direction of observation of his apartment and waiting for a person to show up at the eastern position I noted.
The person, his friend, showed up, at night at the time and date I forecasted, and watched his friend's apartment. We were right behind him. He jumped when we confronted him, so we cornered him, asked him what he was doing there so late at night, and checked his pockets. My client found his keys. The guy was scared out of his wits and we told him that we were watching him watching his friend's apartment.