Wheel throwing is four operations in a fixed order: wedge, centre, open, pull. Almost every problem a beginner has belongs to one of them, and knowing which one is failing is most of the way to fixing it.
Wedging, which is not optional
Wedging makes the clay even in stiffness and removes air. A lump with a hard core and a soft skin cannot be centred by anyone, and the failure feels exactly like a technique problem. Clay straight from a sealed bag needs little; reclaim needs proper wedging, and skipping it accounts for a large share of impossible sessions.
Centring
The clay is pressed down and inward until it runs true, and the technique is bracing rather than strength: elbows locked against knees or the wheel frame so the arms cannot wobble, steady pressure, and letting the wheel do the work. Most beginners use too much water and too little brace, and the clay slips rather than moves.
Opening and pulling
Opening presses a hole down the centre to the floor thickness you want, leaving enough clay in the base. Pulling raises the wall in several passes, each with even pressure inside and out and each slower than feels natural. Too much water and too fast a pull are the two ways a wall collapses.
Trimming, later
When the pot is leather hard it goes back on the wheel upside down and the foot is trimmed. Too wet and it distorts, too dry and the tool chatters. Getting that timing right is a separate skill from throwing and is where a thrown pot becomes a finished one.
Questions people ask about wheel throwing pottery
Why can I not centre?
Most often unwedged clay, too much water or unbraced arms. Bracing elbows against knees or the frame fixes more centring problems than strength does.
Why does my wall collapse?
Usually too much water softening it, or pulling too fast. Fewer, slower pulls with the water wiped off between them.
When do I trim?
At leather hard, when the clay holds its shape but still marks under a thumbnail. Too dry and the tool chatters.