I believe in being pleasant to everyone and simply explain why, nothing is for free. If you kick out all those who ask for something for nothing, you'll end up with very little left over. Remember, you want to be friendly with all clients, someday they could all be paying clients.
Until you get a paying customer, you are going to be dealing with a few that are more than likely "getting their jollies" while they watch you. You can't prevent them from doing that. You just have to try to be careful not to give them too much. If they want to see something really good, they have to pay for it.
I'm usually nice to them at first, and if they persist then i remind them that this is my job and i'm a person. haha, i usually ask them if they'd fix my toilet for free if they were a plumber for 'five gold bb'. if they're really being unreasonable or rude i'll remind them that 'this isn't the food pantry, if you want to see you can pay me'. which usually makes the other guys in the room who do intend to pay, or at least aren't being pricks laugh. I've def earned myself some favorites for being real to the jerks instead of just kicking them out.