A some words of advice... Practice..... Allow youeself about 12
hours . Keep the first hollow thing you make then do not keep
any others until you can throw a cylinder about 8" tall. If the ball
of clay goes off centre too badly, cut it off and start with a new
lump.. Don't wast time trying to recover a wobbly bit of clay..
Keep you elbows tightly clamped on the rim/frame of the wheel. Apply
pressure with the heel of your hand not the inside of your knuckles..
And... Then when you have been trying for the 12 hour, the potters
will tell you the magic words we whisper over the clay to make
it stay centred!!!!