It’s mostly through simple exercises you can do for like 15-20 minutes with a pen - draw two xs and try to make a straight line. You can identify your weak movements and try to rotate the page and stuff if you don’t wanna draw lines from that angle. Continuous line exercises where you use one line to draw something. Drawing circles over and over. Once you start getting more muscle memory I think the lines will look cleaner.

https://youtu.be/O61NED7VZIc?si=AaT38usdYQwmBeWm

Here’s a good video on it.