See This article.. i hope this article help for you : http://www.rss-specifications.com/create-rss-feed.htm
What kind of platform you use to build your site : wordpress, blogger? Wordpress and Blogger and other blogging platform automatically create RSS. Usually you just need to click RSS icon in browser address bar. If the platform does not provide RSS, you can create it using this free RSS creator : ice rocket rss creator (type "icerocket rss" in google search bar)
You can also create RSS feed manually & there are many sites to create rss feed..search on the internet
The easiest way to create an RSS feed is to use software. The software I would recommend is FeedForAll (there is a Windows and a Mac version). There is a built-in wizard that will walk you through the process of creating a feed. You can download an evaluation version from http://www.feedforall.com If you prefer to create the feed by hand this website details how to hand code the RSS feed http://www.make-rss-feeds.com Best of luck!
There are several ways to create a Rss Feeds for your blog, Actually it depends upon what sort of platform you generally needs, Either it is Blogger, wordpress or any other.. most blogging platforms allows you to create RSS Feed automatically..