.:173/365: The Biddle Trick:.
This routine is one of the easiest card-upside-down-in-deck routines simply because even the name of the routine gives you an idea what it takes to do it.
As a street magic routine, this is completely impromptu. It requires zero setup, zero gaffs, and minimal sleights, to say the least. Very quick to execute, very straight to the point, and has a nice little script for you to play around with.
Personally, the Biddle trick is something I would use if there’s no way for me to spread cards on a surface for me to do a more elaborate Triumph-style routine. I believe it’s more effective to use the Biddle routine as it appears to happen right in the hands of the person you’re performing it for, which just adds to their shock and consternation when things do come to a head afterwards.
There isn’t much I could say about this one except you really should learn it, and the mileage you can get out of it is rather significant.