Do you believe in what you're doing when you perform a magic trick? What is the story you're trying to tell?
If you're going to make something vanish, for example, the natural question that will arise in someone's mind is, (of course) "how?" and then "where did it go?". If you don't have an answer for these questions, you don't have a fully fleshed out story. To paint a picture of mystery when performing, one absolutely must believe what they are doing is real to some level. In the very least, be a convincing liar.
If you're telling a lie, and you don't have the details straight, people will sense something's not quite right. They won't believe. Magic is the same way.
Maybe you don't know. Maybe this power you've discovered is new to you. Maybe you're still trying to figure it out.
Here's an idea. Write out a fake scientific explanation for what happens when something "vanishes". Invent a place that it goes, method of transport, molecular makeup, whatever you want. The important thing isn't whether it's plausible, but that you have a clear idea of the whole story.
Where you look, they look. What you believe, they believe.
