Use the links below to re-style this entire web site to see how you can change the looks of a website with CSS while leaving the content in tact.
Semantics is using language structured in a meaningful way. It's having content in a hierarchy. It's not using h1's to make something big, it's using h1 as a primary heading (or title). Then things in that section fall under that heading or title.
Think of semantics as an outline of what you're trying to convey. Group things appropriately and consistently.
Order your lists with a purpose. If there is no specific reason to put one thing before another, then order your lists alphabetically. If you're showing steps for something you'll probably want to use an ordered list via HTML like this:
If you're listing things that aren't 1, 2, 3, etc., then use an unordered list via HTML like this (still use some order though like listing things alphabetically):