Start with a shared campaign
Facebook and Instagram can share a campaign objective, audience and publishing window. Put those decisions in one master item. This prevents duplicated planning while leaving enough room for a channel-specific message.
Write different variants
Facebook often benefits from context, links and a question that starts a conversation. Instagram needs a visual first impression, a concise caption and useful hashtags where they genuinely help. The same announcement can therefore have two different texts and media selections.
Select the right media
Do not assume a landscape image or a long video works everywhere. Validate the chosen image, video or reel against each target before approval. If a variant is incomplete, keep that channel out of the scheduled publication instead of risking a last-minute failure.
Schedule with ownership
Set one campaign date, then confirm the individual publication time and approval state per channel. A failed Instagram variant must not stop an approved Facebook post. Conversely, a success on one channel is not proof that the other one published.
Review the result in context
After publishing, compare reach, engagement and meaningful actions by platform. Use the result to improve the next variant, not to force the same creative choice everywhere.