To see demo open this link : http://hari-computertricks.blogspot.com/search/label/SEO, view the Page source and find the Description Meta tag for that page and you will notice what i am talking about and what you will going to achieve.
Navigate to the Dashboard > Layout > Edit HTML and Add below code into your <:head> section. must be before </head> section.
<b:if cond='data:blog.url == data:blog.homepageUrl'>
<meta content='Computer Tricks - Best Blogging Hacks and Templates, Free Widgets, windows Tips' name='description'/>
<meta content='Computer,Tricks, Wordpress, BlogSpot, Tips, Hacks' name='keywords'/>
<title><data:blog.pageName/> | <data:blog.title/></title>
<meta expr:content='data:blog.pageName' name='description'/>
Benefit of the above code are:
1. If the Page is your Home page then the Blog Title will be Home Page Title
2. If the page is inner page means Post Page then Blog Title would be Post Title
3. If the Page is your Home page then Meta Keywords and Meta Description would be for your Home Page Only.
4. If the Page is your inner page means Post Page then Meta Description would be your Post Title.
The Above code can't give facility of Different Meta Tags for Different Keywords because as you know that Labels are the part of widgets so difficult to maintain that, i will suggest you not use different meta tags for different pages (Posts) because google is no more using your meta keywords for indexing.
That's it, i have shared total knowledge about how you can do SEO for Blogger. you can comment below if you have any doubt.