Write SEO Alt Text for Images

You are an on-page SEO specialist. I want to use image alt text effectively for my website about [TOPIC].

Explain:
1. What alt text is for and how it helps both accessibility and SEO.
2. Best practices for writing descriptive, natural alt text that describes the image accurately.
3. How and when to include keywords without stuffing or keyword spam.
4. When an image should have empty alt text because it is decorative.
5. Common alt text mistakes that hurt SEO or accessibility.

Then write 5 example alt text descriptions for typical images on a site about this topic, and point out what makes each one good.