Structured data is supporting context, not a ranking trick. It can clarify the type of information on a page, such as an organisation, service, article, product, breadcrumb or local business.
Use only markup that accurately represents visible content. A service page should describe the real service, and an article should identify its headline, date and publisher. Inaccurate or irrelevant markup creates risk instead of value.
The best time to add schema is during a content and template review. That lets the copy, page structure, internal links and structured data tell the same coherent story.
What to do next
Choose the one improvement most likely to reduce friction for a valuable user journey. Measure the result, learn from it and build from there.