Step 1: XML Declaration

Since RSS 2.0 must validate as XML, the first line in your rss feed must be the XML declaration.

The encoding is optional but recommended. If your using something other than UTF-8 be sure to change the above line.

Note: If you are using CFML and have whitespace due to the Application.cfm file you can reset the output buffer using 

Step 2: RSS Channel

In this step we need to open up the rss tag, and the channel tag, all of your feed content goes inside these tags.

Step 3: RSS Feed Information

Next you place information about your RSS feed such as the title of it, the description, and a link to the the site.

The title of my RSS 2.0 Feedhttp://www.example.com/This is my rss 2 feed descriptionMon, 12 Sep 2005 18:37:00 GMTen-us

The lastBuildDate should be the date and time that the feed was last changed. Dates in RSS feeds should comply to RFC 822. In CFML the DateFormat mask would be ddd, dd mmm yyyy and the TimeFormat would be HH:mm:ss. Dates should be offset to GMT. The lastBuildDate tag is not required but is highly recommended.

Step 4: RSS Items

Next we enumerate over each RSS item, each item has a title, link, and description, publication date, and guid.

Title of an itemhttp://example.com/item/123http://example.com/item/123Mon, 12 Sep 2005 18:37:00 GMT[CDATA[ This is the description. ]]

Make sure you escape any characters that might cause your XML to invalidate, these characters include , & - I like to enclose any content that may contain HTML inside a CDATA section.

Note: In CFML you can use the XmlFormat function to escape special characters in XML.

Step 5: Close Channel and RSS tags.

Step 6: Validate your feed

Validate your feed using FeedValidator.org.

Other things to take note of

• Content Type - See my post on content types for RSS feeds
• Encoding - You should include the encoding in your Content-Type HTTP header, and in the XML declaration.
• Styling - If you want to make your RSS feed look a little nicer you can CSS stylesheet for your RSS feed.
• Categories - It's a good idea to include category tags in your RSS feeds as well, these go inside the item tag. You can give an item multiple categories by adding a tag for each one.

I have just scratched the surface of what you can do with RSS feeds, so check out the RSS 2.0 Spec for more info.