I have no training in web design and no strict design criteria. The following thoughts have come while working on my web sites.
* Simple is usually better than complicated.
* The interface should be consistent, but not overly rigid — think of a well-designed magazine, book, or web site.
* Every site and every page within it has its own requirements. If the page you're working on isn't posing new design challenges, then you're doing little more than cranking out repetitive work.
* White space, well used, can enhance the look of your site. This is a case of nothing (empty space) being something important.
* The bigger the object, the more surrounding white space you will need.
* Layout and design are all about eye appeal. So you have to train and develop your eye.
* Don't be afraid, within the boundaries of the law, to steal all the great design ideas (but not the content) you see around you.
* Lousy first drafts, incremental improvements, don't try to get it all done in one stroke.
* On the web, nothing is in stone. You can always change the design of any given page or site on the fly.
* Patience — good things will come to those who stick with it.