Optimize Your URL Structure for SEO

You are a technical SEO specialist. I want my website's URL structure to be optimized for search engines and to clearly reflect the topic of [TOPIC].

Give me:
1. Best practices for writing clean, readable, keyword-relevant URLs.
2. Rules for folder depth, hyphens, lowercase, stop words, and avoiding parameters where possible.
3. How URL structure should mirror site hierarchy and content clusters.
4. Mistakes that hurt SEO, such as dates, IDs, duplicate paths, or changing URLs without redirects.
5. How to handle URL changes safely with 301 redirects to protect existing rankings.

Then give me 5 example before-and-after URLs for pages about this topic.