To create blog excerpts, under your blogs posts, on the main blog page, in WordPress 3.8.1 +, follow the instructions below.

How to create blog post preview text

1. Go to your blog post 'Edit Post' page.
2. Click on the 'Screen Options' tab at the top of the page.
3. Check the box that says 'Excerpt'.
4. Input your excerpt text into the new 'Excerpt' field that appeared.
5. Save your changes by clicking the 'Update' or 'Submit' button at the top right of the screen.