The riffle shuffle is one of the best card shuffling methods. Mathematicians have done maths to determine that just half a dozen riffles usually provides acceptable randomness throughout the deck, if done properly.
A lot of people don’t like it because it bends the cards. It’s worth pointing out that while the “showy” shuffles with a flashy finish will bend the cards quite severely, it’s quite doable to riffle a deck with only minimal bending on the corners that doesn’t leave any permanent damage.
Regardless, here’s a simple method for performing a riffle (technically more of a weave, but with less effort) that involves absolutely no bending whatsoever. It’s trivially fast, easy, and done entirely in your hands – very effective for fidgeting when reading slabs of text anywhere.
Step 1: hold the edges of the deck between your thumb and fingers. Either pair of edges will work, but holding the short edges probably makes the most sense.
Step 2: hold the other pair of edges between the fingers of your other hand, then slant the deck to the side. Ideally the bottom should migrate to base of your thumb.
Step 3: splay the bottom of the deck outwards by rotating your hands upwards while keeping pressure with your thumb.
Step 4: pull about half the cards out with your other hand. You should be able to maintain the splayed structure.
Step 5: push the splayed edges into each other. You might need to slide them back and forwards a bit, but the two halves should fit together with very little effort.
At this point, just square up the edges and you’re done. The main problem with shuffling like this, as with any in-hand shuffle, is that the bottom cards can be revealed if you’re not careful. A cut or two on the table surface is always good practice for any shuffle.
And now I feel like I must have illustrated WikiHow pages in a former life…