When I used a CB convention was start at channel 19. This is like a general chat area to catch up on road news - if you pick up someone to talk to then move to an other channel for your chat clearing the air ways for someone else.
Channel 9 was for emergency calls only.
Beware that anyone can listen to your chat it is not like this forum when you got to PM’s. Anyone can listen to any channel if they want
Hope this helps.