I used to use WordPress a LOT and for the most part, I used the exact same starting plugins for almost everything. Plugins that help with stuff like SEO, Sitemaps, and a few set-it-and-forget-it type of plugins. I use almost all of these on every new WordPress install, and have never had any real problems with them and they all work great.
This provides pretty much all you need in terms of SEO for your WordPress site. It allows you to customize your meta data, your page title format, how links look on search engines, and you can even allow custom settings on certain posts/pages. It’s a great set-it-and-forget-it plugin that you only need to fiddle with once and then never again.
This plugin provides everything you need to get your WordPress site working with Google Analytics. It provides settings like watching for certain file types (I watch the .mp3 file type), not tracking certain types of users (ex. if you’re an admin, don’t track your activities on the site), and even has a custom dashboard widget that shows a graph of your current unique views (I use the dashboard widget all the time). It’s a great little plugin that does everything and I have no complaints about it in terms of setting it up.
This generates and sends a sitemap of your site to Google, Bing, and other search engines. You can set it to generate a new one on every new post, or generate one manually. It does one thing, and it does it extremely well.
This creates some share buttons to Google, Facebook, Twitter, Reddit, and a bunch of other social networks on your posts. You can put the buttons anywhere in your post (I have mine at the top) and they all work great. You might need to fiddle with the width of the buttons, but it’s all done within the plugin settings so it’s pretty easy for anyone to mess around with. A great/easy way to throw a share link on any/every post.
Honorable Mention: WP-Syntax
This creates a CSS class that you can wrap around code snippets for syntax colouring. It supports a ton of languages, and you can define your own styles too. I use it for all code snippets on my blog (AND YOU SHOULD TOO!).