How to Keep a Post Always at the Top of your homepage.

Sometimes, you may want a particular post to be at the top of your homepage, say, for a specified period of time, especially if you are using the post to promote a product or service. And you want it to be seen first whenever a visitor visits your site.

Although Blogger arranges posts order according to their date & time, you can still change your post time to keep it at the top as long as you wish.
To do this, follow the steps below:

When writing the post,just click the Post Options link at the bottom of the post editor and change the date of the post to some future date . The format of the date is Month/Day/Year like when I'm writing this post, the date is 7/15/09, so I can change 09 to some future year.

If you've already written and published a post then you can go to Edit Posts and then find that post. Once you found it, click Edit link and post will again open in the Post Editor where you can change it's date.
when the future date you specified reaches, you can change and fast-forward it again.