Here's a list I've compiled of completely useless, meaningless habits magicians have adopted over the ages.
WHY do magicians always riffle the deck with the tension of breaking a bird's neck?
WHY do magicians have the annoying habit of looking smugly into the audience after doing something impressive? We get it, you're good and you know it.
WHY do magicians make stupid noises with their mouths when something magical happens? Particularly smacking their lips or cracking their tongue when something vanishes.
WHY do magicians like to show off crazy finger maneuvers and exercises during their acts? Combine this with the smug look into the audience thing and you've got the perfect was to non-verbally say "I'm really amazing at pleasuring, meet me at the stage door after the show if you're single, hot, and female"
Here's a full WHY story: I once saw a young magician who spent 5 damn minutes (no exaggeration) pulling random shit out of a Square Circle Production prop. Silks, bottles, coins, you name it. Nothing was justified... not to mention the kid had the absolute worst magic soundtrack I've ever heard. At one point, he produced a length of rope from the Square Circle, and in displaying it briefly lifted it to his throat with both hands and, for a split second, pretended to strangle himself with it. It was the whole works too... bulging eye balls, tongue stuck out at the side... had he started to turn blue I would have jumped up to rescue the poor lad from committing suicide on account of his awful magic act.
WHY DID YOU DO THIS? Doing stupid things like wiping your mouth with silks you produce and strangling yourself with rope serves NO DRAMATIC PURPOSE WHATSOEVER. It's not clever, interesting, or funny... just confusing. Everything you do in an act or even just an effect must be motivated. The whole act I described served no purpose... the magician produced a random assortment of pointless items, none of which were clever in the slightest. If you're going to produce objects for no reason, at least connect them logically.
Although, the most powerful theatrical use of making something vanish or appear in terms of justification is, simply, purpose! Produce things because you NEED them. Vanish things that you no longer need or want. Consider Soma... he has a positively brilliant, award winning act involving, primarily, the need to make a phone call. At first, all he has for himself is a payphone. So, for good reason, he produces coins! Coins to pay for the phone call! Logical and justified. Earlier on in this same act, he restores a torn newspaper. Not just for the sake of doing a magic trick like many, but because he accidentally tore it and wants it back in one piece!
So, in constructing an effect or act as a magician, consider this: "You have a real, human, logical problem. If you could do magic, how would you solve the problem?". Ask yourself this question and you'll have the key to creating connecting, strong, interesting, justified magic.