I use fluid widths where possible. I also try and build the page so it will be usable at 640 x 480! not always successful, as you can imagine. So I make sure it looks OK at 800 x 600 and font size increases don't break it too badly.
I still haven't figured out the right thing to do for visitors with hi res screens. My paragraphs run right across the screen and are probably difficult to read.
Maybe I should put a little notice like "if the sentences are too long, resize your browser window!".
Have alook at the sites you admire. Resize your browser window a few times on each. Figure out what you like. Imitate. :x