So we have a new page, we've added a link to the Quick Launch so we can easily find it... but the page is still pretty ugly:

Well, the first thing we can do is apply the SharePoint styles to the page.  This will work if you want a completely custom layout for your page but still want to have a consistent style.  Open the custom page in SharePoint Designer and choose "Manage Style Sheet Links" from the Format --> CSS Styles menu:

Ensure that "current page" is selected and click Add:

Paste in the relative path to SharePoint's core CSS file:  /_layouts/1033/styles/core.css

Press OK and save the page to commit your changes.  Now when you reload the page, it looks much more like a SharePoint page: