I actually studied astrology for a time, but I found the rules to be almost random, so full of gotchas and exceptions that you can predict anything from anything. If there is anything to it, it probably has to do with typical environmental conditions during gestation and birth. I once asked this question of an astrology instructor, who said that was not the case, it was really "the stars". I also tried comparing published horoscopes of people born in the tropics and the southern hemisphere, but perhaps not surprisingly there are quite few of those.
I'm a Capricorn with Gemini rising. In some ways I'm a perfect exemplar of that strange mix, but again the rules are so godawful that I think you could fit anyone into any horoscope without violating the rules. I can discuss how people match up to their signs fairly well. I tend to treat it as a form of entertainment rather than actual prediction.