1.) It really depends on the type of website. I rarely, if ever have the blog on the first page. I usually always dedicate a separate blog page and have the index or main page be different then the blog, widgets, sliders, etc.... You can change the default "Homepage" and blog in Settings>Reading (wp-admin of course)
2.) What do you mean by correct markup? How do you re-write the way the blogs are displayed? Sorry, the question was just a bit confusing for me.