Ok so you're new to this style of routine. That's fine.
I'm assuming you meant no harm, and just don't yet understand how the magic world really operates. Quite possibly you've come from Instagram and YouTube where people frequently give away secrets they have no rights to reveal. But if you're going to take magic seriously, that's not a practice to indulge in.
People who come up with these methods, particularly the good mind reading routines, tend to be either professional performers, or at least people who sell to performers. So, by asking for us to give you the technique for free, you're asking for us to give away a portion of someone's livelihood for nothing. Can you see why that's a problem?
So - you want to learn how to guess passwords. Do you have a link to the video you mean specifically?
The place I recommend starting to learn these skills is always Bob Cassidy's Fundamentals. It's an eBook and not terribly expensive. It teaches you the foundation skills for mentalism and mind reading. From there you'd want to check out Practical Mental Magic by Annemann, and then on to Fraser Parker and Peter Turner's material. If you're feeling bold you could just start with Turner and Parker's stuff - but you'll have an easier time of it if you understand the foundations they are working from first. Oh yes and 13 Steps to Mentalism, after Fundamentals. And if you're loving the genre, The Artful Mentalism of Bob Cassidy is good, too.
