In my experience with HTML and HTML5, I've used various elements to structure a simple webpage effectively. The most useful tags for me have been the semantic tags like <header>, <nav>, <main>, <section>, <article>, and <footer>. These tags help in organizing the content in a meaningful way, making it easier for both developers and browsers to understand the structure of the webpage. For instance, the <header> tag is great for containing introductory content or navigational links, while the <footer> tag is perfect for footer information like contact details or copyright notices. Using these semantic tags not only improves the accessibility of the webpage but also enhances SEO, as search engines can better interpret the content.