This is almost too easy. Octopress already comes with basic integration options built-in.
See here for more details than I care about, but the short version is that you just have to edit
_config.yml and fill in fields for your Google+ username, a true/false value indicating whether users can share your posts on Google+/Twitter, a Disqus shortname for comments, a Google Analytics tracking code ... you get the idea.
(though there seems to be some extra work required to get Twitter to show up in the sidebar.
While we're at it, might as well change the theme too. There's a huge collection of options at OPThemes. So, pick one and replace the default dark grey one!
The usual flow is something like
git submodule add <the theme's git repo> followed by
rake install["<the theme name>"]
octoflat which doesn't have a sidebar, but is otherwise pleasing to look at.