RSS feeds are created in XML. Feeds can be created using tags that are enclosed in brackets <> very similar to HTML.
Software to Create Feeds
If you are not as confident and would like software to create the feed we strongly recommend FeedForAll an extremely easy to use feed creation tool that allows webmasters to create, edit and publish rss feeds.
If you want to create an RSS feed using a text editor a step by step walk-through at Make RSS Feeds will help.
Online Feed Creation Tools
If you just wish to create a single feed and do not need to edit or update the feed you can use an online feed creation tool.
GoArticles - Syndicate articles appearing on GoArticles a large article repository.
BlogStreet - online feed creation tool, only works for blogs hosted on BlogStreet
: