Have a specific form in mind when you weigh your clay and sit down at the wheel, and work toward that.
Try to make 6 inch cylinders from one pound of clay. Realistically you’re not going to do it (it’s not easy, I couldn’t probably do it consistently) But it gives you a goal. You want even pulls and consistent thickness the whole way through.
Make 10/20/50/100 whatever, just make them. You can recycle clay so you only lose whatever Slip you toss from your bucket. Wedge yourself ten balls of clay to start all the same weight and try to make each cylinder as tall and consistently thin as you can, even if it eventually collapses.
Deliberately vary your technique. After throwing each piece, assess where your shortcomings are (too thick at the base? rim is too thin? bowl slumped?) and make a plan for improving on the next piece. Just repeating the same process over and over without changing anything won’t help you improve.
Do not spend too much time agonizing over every single piece at the wheel. If you mess it up, spend a couple minutes trying to fix it (cut off a wobbly rim with the needle tool, try to bring back a slumped or warped pot), but don’t sit there for an hour playing with a messed up piece of clay that’s warped, water saturated, and off-center. Cut it off, cut it in half, and work on doing better with the next piece. This is one place I see people really get stuck at my studio.
Beginners will come in and throw for 15 minutes, mess something up, and then they may spend their remaining 2 hours 45 minutes trying to fix one piece of clay.
You can also watch the excellent Hsin Chuen Lin, other YouTube channels to watch are Ingleton Pottery, Simon Leach, and Bill van Gilder.
If you’re looking to improve quickly, the most important thing is to throw as much as possible. Prepare as many balls of clay as you think you can throw in one sitting, wrap them up in plastic, get on the wheel and throw. Like everyone else says, cylinders are a good place to start.
Clary Illian’s “A Potter’s Workbook” might be a good book to look & work through. It covers a lot of the basics of form.
Things to try/think about while throwing:
- Different styles of placing the clay on the wheel (a perfect sphere, an awkward lump, flat bottom or pointed bottom, sealing the edge with water vs not, pounding it onto the wheel)
- Different styles of centering (keep an eye out for how other people center)
- Different styles of opening (thumbs or fingers, 2 handed or 1 handed, with a fist, outwards or inwards, starting at different heights)
- Different ways to pull (different fingers, fingers tips, knuckles, using a sponge or shammy, different angles, 1 handed [on the first pull], locking your hands together vs keeping them separate)
- Keeping your movements steady (locking your elbow to your torso or pressing it into your thigh)
- Sitting different distances from the wheel (I like to be as close as possible because it helps me keep my hands steady)
- Pulling large amounts of clay (getting >50% of your height on your first pull)
- Changing your wheel speed
- Different bottoms (generally curved for bowls/plates, and flat for cylinders)
- Different styles of compressing the bottom (using a rib or your fingers, crossing the center as you’re compressing, going outwards to inwards or vice versa)
- Different styles of compressing the rim (using the edge of your fingers, using a sponge, using the space in between two fingers, using a rib, using a shammy)
- Using a rib to smooth the sides vs using your fingers
- Pulling as high as you can
- Intentionally creating an uneven wall (e.g. leaving extra clay at half height)
- Playing with the lip (flaring it out, collaring it in, folding/rolling it over, playing around with the way its beveled, making it thinner/thicker)
- Different styles of foot (vertical, cut inwards vs outwards)
- Different moisture contents of clay
- Different thicknesses of the bottom