I was searching google for my site:domain.com and noticed many of my pages didn’t get indexed with nice titles. I wanted the format to be something like Post Title - Site Name on pages, posts and tag pages and just Site Name on the index page. I updated default.hbs with this line which did that and figured why not share in case others want to do the same. 
<title>{{#is "post"}}{{meta_title}} - {{/is}}{{#is "page"}}{{meta_title}} - {{/is}}{{#is "tag"}}{{tag.name}} - {{/is}}{{@site.title}}</title>