A twelve-minute video I found at two in the morning, made by someone whose channel had maybe six other uploads, is the reason I ever tried drawing without looking at the paper. The comments underneath it were mostly about a totally different video that had autoplayed next, not this one. I tried the exercise anyway, on the back of a phone bill sitting on my desk.
Your first day
Starting takes ten minutes with a mug and a pen. Any pen that doesn't skip and any paper works. Expensive materials mostly just add unnecessary stress before you need them. Set a mug in front of you. Start anywhere on its outline and keep the pen moving slowly, tracking the actual edge of the object with your eyes and not looking at the paper until the line has gone all the way around back to where you started. It will look distorted, which is expected. Don't lift the pen even when the line goes somewhere unexpected.
Glancing down at the paper constantly to check the drawing is the habit to avoid. That's what produces the stiff, overly careful lines beginners dislike about their own work.
The thing most people miss
I assumed drawing well meant having a steady hand, and that shaky lines were simply a sign of not being good yet. What actually changed my understanding was noticing that my wobbly, uncertain lines from this exercise usually captured the mug's actual proportions better than my careful, constantly-checked attempts ever did.
Once I started doing this kind of looking-heavy drawing before anything else, it made the real drawing that followed looser and noticeably more accurate, not just faster.
How you'll know it's working
A week or so in, a line drawn without glancing down once will actually match the object's real shape closely enough to surprise you. Holding a finished sketch next to an early one makes the difference obvious immediately.
Eventually, looking this closely at an object stops feeling like an exercise and starts feeling like just how drawing is done. From there, basic value shading, using darkness and lightness instead of only outlines, is what starts giving these same loose lines an actual sense of form.