As already stated, screen -S SESSIONTITLE works for starting a session with a title (SESSIONTITLE), but if you start a session and later decide to change its title. This can be accomplished by using the default key bindings:
Ctrl+a, A
Which prompts:
Set windows title to:SESSIONTITLE
Change SESSIONTITLE by backspacing and typing in the desired title. To confirm the name change and list all titles.
Ctrl+a, "
