This one is very simple. But to me it makes a world of difference. It is a pet peeve of mine to go to a blog, and see all the widgets in the sidebars aligned left! Even worse is when some are centered, and some aren't. So in order to make them all nice and sexy - do this:

While pasting the widget's or button's HTML code into the "Add HTML/Javascript" window - type this BEFORE all the code:

Then type this AFTER all the code:

Simple! And makes your blog SO much more uniform and nicer-looking!