There's no one-size-fits-all answer to this question, as the ingredients of a successful PR campaign will vary depending on the goals and objectives of the company.
A successful PR campaign should also be tailored to the specific audiences that the company is trying to reach. For example, a tech startup will have different communications needs than a major corporation.
However, there are some common elements that all good PR campaigns share, such as:
Clear objective or goal
Strategic planning
Creative thinking
Thought leadership
Media relations
Crisis planning