when it comes to the balducci, it's all about presentation... if you just say watch this, and levitate. You probably have about a 75% chance of getting caught. Here is my own personal style on the trick:
First off, I perform it from the front with my heel rather than from the back with my toe (this is probably exposure, but really, who doesn't already know it anyway). This seems to be more convincing and more motivated, because why would you need to turn your back to levitate? you would most likely face them. Anyway, it is a lot more difficult with your heel, takes a lot more balance, so practice practice practice. Also, I have them hold out their hands palm up, and I place my hands on their's palm down. I tell them to think the word lift on the count of three, and to slowly lift me off the ground. while I'm up I rotate slightly to one side, and then back (this takes a LOT of friggin practice). and then I tell them to clear their mind and when they do, I drop. I have used this presentation to fool people who knew the balducci. try your own presentation methods, or steal from me a little. Just don't say 'hey look' *levitate*... build the tension, take deep breaths before you levitate, act drained when you come back down. Balducci can be a killer self levitation if it's presented correctly.