If you are using WordPress, than its better to use JetPack Publicize to share your posts on social media with great options
Well, depends on the platform of your blog. There are many plugins that tweet your new posts. Even Twitter's official plugin does it, so check it out. If you are using Wordpress - the choice is big, so try some
As a WordPress user, I like (and use) the free WP to Twitter plugin available here: http://wordpress.org/plugins/wp-to-twitter/ It gives a lot of flexibility, the ability to customize the format of the auto-tweet when you post, and even incorporate a custom URL for tracking.
twitterfeed is nice if you got a blog with rss simple and not dangerous as some auto tools when they are badly used