How to adding different meta descriptions to different Blogger Posts?

Exactly what is the use of adding different meta descriptions to different Blogger Posts?

It is quite good for SEO (Search Engine Optimisation). Actually, why we are incorporating meta tags is to tell search engines what that page is focused on... but , using same meta tags to all of your respective blog posts lessens the search engine rankings and traffic little bit.
But , if you add different unique meta tags to different Blog posts, it creates the search engines to know more about your individual blog posts and make these crawl and index your pages better and it also improves your Search engine rankings for certain; )

So , how to add this?

For this to happen, you have to add some pieces of codes to the web template.
First Sign in to Blogger dashboard » Layout » Edit html page and find this line

and add this code just below that line

<b:if cond='data:blog.url == "http://www.bloggertipandtrick.net/"'>

<meta content='DESCRIPTION' name='description'/>
<meta content='KEYWORDS' name='keywords'/>

</b:if>

Now we have added meta tags to the homepage.
Next, you want to add meta description for your blogger post, for example let see how to add meta tags to below post :
http://www.bloggertipandtrick.net/2009/03/how-to-add-paypal-donate-button-to-your.html
This is the way to add meta tags to above post:

<b:if cond='data:blog.url == "http://www.bloggertipandtrick.net/2009/03/how-to-add-paypal-donate-button-to-your.html"'>

<meta content='How to add Paypal Button to your Blogger Blog, Adding Donations to your blog' name='description'/>

<meta content='Adding,Paypal,Donate,Button' name='keywords'/>

</b:if>

Now, what you have to do is pasting the above code below the home page meta tags and changing the link,description and keywords.
So, the final code now looks something like:

<b:if cond='data:blog.url == "http://www.bloggertipandtrick.net/"'>

<meta content='DESCRIPTION' name='description'/>
<meta content='KEYWORDS' name='keywords'/>

</b:if>

<b:if cond='data:blog.url == "http://www.bloggertipandtrick.net/2009/03/how-to-add-paypal-donate-button-to-your.html"'>

<meta content='How to add Paypal Button to your Blogger Blog, Adding Donations to your blog' name='description'/>

<meta content='Adding,Paypal,Donate,Button' name='keywords'/>

</b:if>

Just like the above procedure, you can add different meta tags to as many blog posts as you can.