How do people (brokers, etc) get concert tickets before they go on
sale to the general public?  I would like to get tickets to Paul
McCartney & I'd like to get them early rather than paying a ticket
agency.  Thanks,.

Fan clubs sometimes give their members access to tickets before the
general public is able to buy them.

They get them by being ticket agencies, or being involved in the
business. In the same way, a shop - and even before them, the
distributors and other parties involved in the distribution and retail
channels - might receive stock of a product before its official
release date, but they won't be allowed to sell it to the public.

As a mere member of the public, you're not going to get tickets early
unless you have some special access to something or someone who does,
and is willing to let you have them. Probably you'll need to be a fan
club member, or win a competition, or bribe someone, or become a
ticket agent.

Thank you for the comments.  Both comments are appreciated.  The
second comment, answers my question in a complete manner.  It's worth
the money for me.

This is my first question.  Already made a typo; I meant getting
concert tickets , not giving.  Since these are comments, I guess I do
not rate them or agree to accept answer & pay (but I would).

Thanks again.