@gerry456 said

" (this is a bit difficult and may put pressure on genitals if male so is it a good idea) "

If you're crushing yourself, it might help to sit with your buttocks on the front edge of the chair such that your genitals are past the point where they can touch the chair.

Love is the law, love under will.

"What am I supposed to be concentrating on: holding the form or a specific thought?"

Baby steps.

Start with asana. Just pay attention to your body and keep it in a firm & steady position. Once you are comfortable with this, you can do mental concentration while in the asana.

"Is it normal for the legs to start shaking in the first minute? "

Yes, if you are unfamiliar with the asana. I assume you are in the God asana in a chair?

"I am assuming that this is just a sign of weak stabilizer muscles and will go away with practice."

Exactly. Persist. Consistency is key. 20 bouts of 10 mintues is much better than one bout of 200 minutes.

IAO131

"Hands on thighs, feet and knees generally (but not invariably) together."

I am just starting out with the big blue brick, and am curious about two things:

What am I supposed to be concentrating on: holding the form or a specific thought?

Is it normal for the legs to start shaking in the first minute? I am assuming that this is just a sign of weak stabilizer muscles and will go away with practice.

"is the God asana back upright in a chair with hands on knees and knees closed together (this is a bit difficult and may put pressure on genitals if male so is it a good idea) or is it hands on thighs with feet apart?"

Hands on thighs, feet and knees generally (but not invariably) together.

IAO131