I prefer a citizen's income which is generous enough that people can make choices for themselves.
How much dosh, what method of payment & would it to be for every person of working age?
In reverse order of your questions:
I would have a single payment system for everyone who is 18 years or over (after completion of school year) and abolish the state pension. Therefore any income from pension schemes would be in addition to the citizen's income. This would be applied on an individual basis and available to everyone to claim between 18 and death.
My system would taper this payment through the tax system. If you claim it then you would pay an additional amount in income tax. If you're earning above a certain level, there wouldn't be any benefit in claiming. There would need to be other simplifications of the tax system required but this would support people in low pay the most and also help start-up businesses.
I was thinking of a single monthly payment of circ. £1,000 or £12,000 per annum. This would minimise the issues with housing costs in the South-East in particular where people on existing benefits would need transitional support and also give an economic boost to poorer areas of the UK. I would abolish NI payments and have income tax start on incomes above £15,000 giving people £3,000 of earning before starting to pay tax as the citizen's income would be treated as income.
In my dictatorship, citizen's income would see the abolition of housing benefit, child benefit, tax credits (working and family), jobseekers allowance, statutory maternity leave etc etc. The only benefit would be for disabilities paid regardless of age based on circumstances (needs tested, not means tested). In this system, there would be no means testing. In short, there would be a large simplification and quite a number of state employees made redundant. You would also see an end to parasitic companies sucking at the state teat like Emma Harrison A4e. Its a huge reduction in the role of the state in people's lives.