You should limit closed interactions with girls. If your sitting in a group okay, or if you are trying to find a Shidduh (going out on a date), then you have to talk and try to get to know each other to see if she's for you. But their isn't really "just a friendship" between guys and girls. Dont let the yetzer fool you and say its just talking, + the Rabbis in Pirki Avot say that anyone who talks excessivly with a female will inherit Gehinnom, and that was talking about one's wife, how much more soo someone who isn't your wife.