Basics of Comments and Commenting
In your WordPress Dashboard visit Settings > Discussion to adjust the comment settings for all new posts.
Default article settings
This is where you'll select to allow readers to post comments on new articles. You can also select to be notified when your post is linked to on another blog and if you'd like to notify other blogs when linking their articles.
Other comment settings
This section allows you to require an Email and Name before a reader can comment, if you'd like them to be registered to the site and logged in, you can require that as well. You can also adjust the comment thread levels and number of comments per page.
E-mail me whenever and Before a comment appears
Set up if you'd like to receive an email anytime someone makes a comment, decide if comments should be held for moderation and approved manually.
Comment Moderation and Blacklist
Use the Comment Moderation section of this page to flag comments as spam by setting the maximum number of links that can appear in a comment. Flag comments with key words to be reviewed first, rather than published automatically.
Comment Blacklist automatically marks comments containing any of the listed words as spam and will not go into a queue for review.
Individual Post Comment Settings
To change the commenting ability for a specific post visit the Post you'd like to change. Be sure in the top right under Screen Options dropdown that Discussion is checked. Then scroll down below the content area and find the Discussion box. Uncheck the box next to Allow Comments if you do not wish for readers to comment on that specific Post.
For additional information about Comments and Commenting Settings please visit the WordPress Codex