In the first place, if you don't have content for a section, you certainly don't need to use it. That's not a problem. If you have a heading/title for a table but nothing else, then by all means, you a <thead> without a <tfoot>. Use what you need and otherwise eliminate extra markup.
In the second, you're raising the larger issues of structure and best practices. I like to structure my page via their headings, that's about the most user friendly way since accessibility tools and web browsers usually allow you some feature to move through the document via the headings. Links are the other key feature to use strategically and thoughtfully on the webpage since links and form elements are the standard tab points in the document.
Last but not least, one of the big thorns in the side of the Web Standards movement is table based design. So unless you're using tables strictly for tabular data, use the more flexible method of divs and CSS to control the structure of your page. There's a reason MS went to great pains to include CSS support in VS 2008. It's much more powerful than controlling your appearance inline. And divs give you the logical control that tables do without imposing that structure visually. You can control the visual representation any way you want including rendering the divs in a table like layout. It's much more flexible.
Whatever you can do or dream you can, begin it. Boldness has genius, power and magic in it. Begin it now.
-Johann von Goethe
When Two Hearts Race... Both Win.
-Dove Chocolate Wrapper
Chroniclemaster1, Founder of www.EarthChronicle.com
A Growing History of our Planet, by our Planet, for our Planet.