Using repetition brings cohesiveness to your design. This simple principle means using the same or similar elements in your composition more than once.
It wasn't until I took a Skillshare class by Matt Vergotis that I realized how fun it is to apply this theory to lettering. You want to find ways to copy similar shapes and swashes amongst your letters. I love puzzles and figuring out solutions to problems, so I really enjoy the process of creating opportunities for repetition in my work.
Tracing paper will definitely come in handy here. You don't necessarily need to replicate the exact shape (because it probably won't work in all instances), but you'll want to get something close. Every so often, I end up with unique details in some letters since I'm looking to apply a repetitive shape; it makes me come up with something I might not have originally. It often takes many quick thumbnail sketches, but it's so satisfying once I finally pinpoint areas in my lettering where I can replicate certain aspects.
By using repetition, your composition will be easy on the eyes and pleasant for the viewer...which I've mentioned before is the end goal. Repeating elements establishes visual harmony in your work. Even though people may not recognize that the same shape is duplicated elsewhere in the piece, they will notice that the whole layout just feels right.
For the image I made for this post, I started out by exploring some different styles (left). I settled on a blocky, cursive look and immediately saw that I could duplicate the shape of the downstroke on the "r" and "n" (top right). After exploring a bit more, I decided to also repeat the closed loop on the "r" and the "o" (bottom right). You probably didn't notice those consistencies at first, but the whole word should feel nice and cohesive whether you noticed the repetition or not.
This concept is a fun and easy way to establish unity in your lettering. It might take many different variations of an idea before you can find details to echo throughout the piece. But once you find them, you'll end up with a more unified composition and possibly even a few different quirks in certain characters that you may not have thought to create before.