First of all, if someone is stealing content from a blog then it is probably an automated process through your RSS Feed.
They will be examining your feed, no doubt a few times each day, to grab new content and keep their site fresh.
Because they are not looking at the content they steal, you have the opportunity to fight back.
So the first step is, do not over react! Part 1 - Set them up Straight away write a new post to your blog about anything that you like.
It can be on topic, or even discussing the fact that you are having content stolen from you.
Give the post an introduction then add a sentence saying that it is written by you and mention your blog name.
Hyper link it back to your website.
Then, when they copy the post they publish the fact that they are stealing from you and give you a link back.
Part 2 - Ask yourself why? Why are they copying from you? Probably to create a lot of content for their blog so that they get a lot of traffic, which creates a Google AdSense income.
So report to Google that they are creating a spam site by copying sites including yours and offer your copied post as evidence! This can be done via the webmaster tools.
Part 3 - 'Steal' their traffic Whilst they are copying your posts you can 'force' some posts onto their website.
Why not write a review of your recent posts? Go through half a dozen posts that you have written recently and that readers have read a lot, describe them and recommend that readers read them.
And the important part - link to these posts within this new post.
You can check their blog to make sure that they are copying the posts with the links intact and if not, give the full URL as the hyperlink.
That way their readers are being directed to your website! Part 4 - Raise a complaint If this bit of fun is not enough for you, then look up on how to raise a DMCA Violation complaint.
Do a whois search to find out who their website host is and send the DMCA Violation information to the host.
And just watch how quickly the copied posts come down - 2 minutes on the site who had copied my posts! And in my case? Well, a month later I went back to the blog that had been copying my posts and I saw a post announcing how well the blogger had done out of Google AdSense whilst they had been copying my posts.
However, that huge income must now have stopped as there are no AdSense blocks on the site.
It looks like by reporting it to Google the blogger's account was closed.