How to spot fake agents
This is really easy. If they are asking for money up front, they are bogus. If they say you have to get headshots taken by their own photographer at a discount rate, they are bogus. If they ask you to do anything un-savoury like taking your clothes off or meeting them in a secluded place, they are bogus. If they want you to call a premium rate phone number, they are bogus. Bogus agents prey on your desire for them to be real, they prey on your hope. So be smart, keep a level head, ask questions and weigh up the facts. If they are really over selling you the dream, think why? If they are reluctant to answer questions or are being vague, think why? If they are putting on any pressure for you to sign anything or hand anything over, think why? No matter how much you want this person to be telling the truth, if they are ticking any of the box's above then they are probably stringing you along.
Normal commission shouldn't be more than 15%, and stage work should be less, around 10% or 12%.
Something else to consider is that literally anybody can set up as an agent. Just because they don't ask for money it doesn't mean that they are a good agent, it just that they aren't stealing from you.
Google them, see what their clients are up to and try to find out how long they have been established. The longer the better in general. Visit their websites if they have one, get an idea of them. Research them.
They should expect you to be in Spotlight and to see a showreel or performance before they offer you representation, if they don't then it's not a great sign; how can they sell you if they don't know what you are like or if you are any good?
If you really can't decide whether to trust someone as an agent or not, ask someone. Call Equity, call Spotlight, call The Actors Guild, call The Personal Managers Association, call a drama school, call anyone until you get some advice from people who have experience. Do NOT sign or hand anything over until you have had time to think and seek advice.