Question

How are buffers prepared?

Answer 1

You take quantities of a weak acid and its conjugate base......in appreciable quantities.

Explanation:

And this is practically achieved by taking a weak acid, and adding (say) HALF an equivalent of a strong base......

For instance, we take a molar quantity of acetic acid, and add half an equiv of sodium hydroxide, we get a buffer whose `pH=4.76`, where the `pK_a=4.76` of the original acid.

See this old answer and links.