first of all, i suggest you get a lot of experience first. agents like to hire people who have experience. maybe enroll in an acting workshop, audition for local plays in your city, and just get experience. when you have enough experience, thats when you can get an acting agent. the good thing about getting experience is that people who also want to be an actor will most likely share infos with you. like if you audtion for like a local play in your city, you might get to work with people who are also trying to get experience and talk about how their planning to get an agent, so you can get your info from them. you can also ask the director, or the teacher of the acting class you enrolled in.
so if you want to avoid scams, go out and get experience, and ask around there. ask fellow actors, directors, or your drama teacher and they'll help you and direct you to the right path