This general rule can be applied to many blogging platforms: Typepad, Blogger, or WordPress.
Basically, to create a post template,
- create a post with you opening or with your signature and closing,
- and then save it as a DRAFT instead of publishing it.
Then when you want to create a new post,
- open the draft,
- Copy everything,
- close the draft,
- create a new post,
- and Paste it in there,
- and continue posting as you normally would.