This is my trick, "Central Intelligence". The value of the perfect Faro shuffle was questioned in this thread, so I thought I'd post a video of a routine of mine that utilizes them to hopefully prove their utility.
It's actually a lot easier than you might think. Take a deck. Cut it where you think the midpoint is. Line them up.
Are both piles exactly the same height? Even one card out will mean one pile is 2 cards more than the other, which is visibly pretty obvious. Shuffle and repeat. Shuffling removes any visual cues that might artificially present.
After not a whole lot of times, you'll see your accuracy improve greatly. It's a matter of teaching your brain to immediately spot the mid-point without having to consciously think about it. Once you got it, practice until it's automagic.