The users always needs to know what to do to begin.
No dead ends. Buttons and quick replies, not typing (especially on mobile).
Drive subscriptions early.
Onboarding is important.
Once the user knows the clear purpose.
Clear sectioning at top level.
Intertwine elements within a section to keep the user moving forward.
Continue to drive subscriptions.
Remember broadcasts are interactive, they draw the user back into the content.
Consider how the broadcast will appear on a phone lock screen.
Let subscribers choose what they want to receive.