“And you end clean” is often given as major plus in trick descriptions, and it is. But it is so much better to start clean and get dirty than vice versa.
The beginning is the best time for the audience to check any props they may suspect if you want maximise the reactions to any trick. This is particularly true for a hobbyist whose friends and family know hasn’t got super-powers.
restrictions and parameters of a trick are established beyond doubt right from the start, that way when you defy them and create magic, they can truly comprehend the miracle.
Here is a common example, you get out a deck of cards and immediately start performing a card trick, a lay person can assume all through-out the routine that a trick deck is being used (it’s annoying but know they exist) and although that isn’t even a solution as such, it removes a large portion of wonder. Their amazement is put on hold until their suspicions can be put to rest, usually by inspections and that is why people get grabby. Only once all is confirmed above board, can they appreciate the magic. But by then the dramatic moment has been lost, the knockout punch has become a limp tired jab.
Therefore, if you do use gaffs of any kind and you want to make your magic as strong as possible you should ring-in the gaff on an off-beat, after everything has been shown to be above board. I’m not a fan of handing items out for inspection per se, so I’d recommend performing a few card tricks with a straight deck first that gets handled or pointing out interesting details of a coin. This will also help you get around the loud mouths, the tipsy and friends who don’t mind pestering you ad nauseum to see the props.