This is now pretty old tweak,  but with this hack, you can choose to display a select amount of text from the beginning of each post as a teaser instead of showing the entire post on the front page of your blog. Then when people want to read the rest of the post, they can click a “read more” link to see the full post. This is very handy if you have lots of long articles all on one page. (Note that you’ll need to have post pages enabled in order to make this feature work.)

Update: Blogger now have launched Read more feature in their blog systems.

Step #1 – Update Your Template Code

First you need to edit your existing code so I recommend copying and pasting it into notepad or any text editor. Also, it’s smart at this point to create a backup of your template just in case something goes wrong. Now do a search (CTRL + F) within the text editor for the following code post-header-line-1. This is the default code that Blogger includes but some custom templates remove or change this code so you might have trouble finding it. If you can’t locate this text then try searching for <data:post.body/> instead. Your template will for sure have this since it’s the tag that actually prints the body of your post.
Now depending on which code you were able to find will determine how easy the next steps will be. You might need to do some detective work first in order to get this working properly in your custom template. The idea is to get this new code into your template before the <data:post.body/> tag. Keep reading and hopefully the explanation will illustrate the concept clear enough so you are able to adapt this hack to your custom template.
Add the following code below the <div class=’post-header-line-1′/> and <div class=’post-header-line’> tags if you’ve got both.

<b:if cond='data:blog.pageType == "item"'>
<style>.fullpost{display:inline;}</style>
<p><data:post.body/></p>
<b:else/>
<style>.fullpost{display:none;}</style>

The result should look something like this:

If you don’t have the default <div class='post-header-line-1'/> tag then your result should look something like this instead. This is how it would be done in the MushBlue Blogger custom template:

Notice in both examples that the code in yellow and the <data:post.body/> tags are the same — it’s just tag above it that will differ based on the template you’re using.
Now let’s add one more bit of code which will actually create the “read more” link in your post. This code will go below the <data:post.body/> tag so copy the following and paste it in. Feel free to change the “Read more…” text to whatever you want the link to look like. Be careful not to delete any other code during this process.

<b:if cond='data:blog.pageType != "item"'><br />
<a expr:href='data:post.url'>Read more...</a>
</b:if>
</b:if>

Yes, there are supposed to be two </b:if> tags in the above code so don’t think it’ s a mistake. The result should look like this:

This code will be the same no matter what template you are using. Just make sure it goes below the <data:post.body/> as shown in the image above.
Now let’s look at what the final result should be. Here’s the updated code block you just worked on all put together:

Ok, you’re all done editing the template code. Paste it back into your Blogger html window and save it. If you get an error, you made a mistake. The most common mistake is to accidentally delete a > or < while pasting in the new code. If it saved successfully, it’s time to move onto the next step and modify a quick Blogger format setting.


Step #2 Replacing Read more by the image or button.
 In the codes given below,

 <b:if cond='data:blog.pageType != "item"'><br />
<a expr:href='data:post.url'>Read more...</a>
</b:if>
</b:if>


Replace the texts in red, with <img src=”http://yourimage.com/imagelocation.jpg”>
Then done now you have read more image button in place of read more text.

Step #3 Applying summary in your post
While you want to create summary of the post after specific paragraphs, click on the broken page button (Located at the right end of the toolbar) in the blogger post modification toolbar.
When you click the button, you’ll get a grey horizontal line on your post page. The contents above the horizontal line will be shown and that one below the horizontal line will be hidden and only is revealed when you click the read more link.

Hope this article was helpful.