They are put together by $pecial intere$t group$ then turned over to their lobbyi$t$. The lobbyi$t$ find Congre$$-critter$ who show intere$t in their bill$ who then present it to the pertinent committee$.
It'$ quite a racket.
In Calif a lobbyist can walk into a legislators offices and enter the bill in Legitech. I have seen them do it.
I would like to talk to you about your bill. Dinner and drinks are on you. And you bring the women.