In a typical workflow, it's not uncommon to build out as much of a site in Mura as you can before spending time adding markup and style to your site. While this is certainly not the only way to work, it can streamline the process immensely (especially if you can get someone else to do it before you get started!). When doing your site build-out it's helpful to try to account for as much as possible, adding:
Once you have as much as you can in place, add whatever known markup changes and additions you'll have. These might include:
Once you have a site structure built out and initial markup additions and revisions in place, you'll spend most of your time adding style by editing the theme-specific CSS files and your site will begin to look like something. By the time you've accounted for all the different styles, your site should be about 90% complete.
From here on out, you'll just need to iterate on the first three steps until your site is complete.