If you're using WordPress, you can easily add LIKE button in ur post by installing this Plugin: WordPress Like Button Plugin.
1. Go to your Blogger dashboard
2. Click on Template in the sidebar, then Edit HTML
3. Click inside of the text area and press CTRL + F (or CMD + F on a Mac) to open up the “Find” text box.
4. Inside the “find” box in the top right corner of the text area, enter this code and press enter TWICE. You want to work with the second instance of it:
<data
ost.body/>
This code acts like the placeholder for all of your post content.
If you want to add your Like button to the top of your posts, add one of the following Facebook codes ABOVE this code. If you want the Like button on the bottom of your posts, add it UNDER this code.
<br/><br/><iframe allowTransparency='true' expr:src='"
http://www.facebook.com/plugins/like.php?href=" + data
ost.canonicalUrl + "&layout=button_count&show_faces=false&width=100&action=like&font=arial&colorscheme=light"' frameborder='0' scrolling='no' style='border:none; overflow:hidden; width:100px; height:21px;'/>
Good luck!