If you define a meta description tag for your home page it will be replicated for all your pages which would be taken as a duplicate ‘meta-tag’ in Google. With the code below you can have different description tag for each page of your blogspot hosted blog.
1.Login to your blogger dashboard-->layout--> Edit HTML
2.Scroll down to where you see this:-
3.Copy the below code and paste it after above code.
Replace PUT IN YOUR COMMON BLOG DESCRIPTION TAGS HERE with suitable description for your blog separated by comma. So if your blog is about Blogger tips,the tags can be blogger tips,tricks,hacks,blogspot tips .....
expr:content= ‘data:blog.pageTitle’ gets replaced by the title of your current page.So when combined with the common description tags, the description tag becomes unique for each page.
4.Click on "Save Templates" and you are done.