Before I continue, if you blog and tweet but do not tweet your blogs, you may be missing out on some excellent exposure.
OK, I will keep this short and simple... There are apps that help the process along, personally, I have found that Google's Feedburner does a great job. Set up is easy, and everything is automated, now all I have to do is post on my blog. Not to mention everything else Feedburner can do for your blogs.
Try it yourself, it's free! Feedburner