By default Blogger does not have a trackback system built in, Haloscan servers as a plugin for Blogger on track back and generates a track back URL for every posts.
For example the track back URL for the previous post "TrackBack Link Building" is as follow
http://haloscan.com/tb/palapple/525951609206523671
Auto Discovery enables clients to auto-discover the TrackBack ping URL. By including a set of RDF code in your post as meta data, it will scan your page and return the client with your track back URL.
Have your Blogger and Haloscan accounts setup properly, then login to Blogger account, under Template tab, insert the following code segment under the comment section of post pages.
<!-- Begin trackback -->
<!-- Auto Discovery RDF Code
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/">
<rdf:Description
rdf:about="<$BlogItemPermalinkURL$>"
dc:identifier="<$BlogItemPermalinkURL$>"
dc:title="<$BlogItemTitle$>"
trackback:ping="http://haloscan.com/tb/haloscan-id/<$BlogItemNumber$>" />
</rdf:RDF>
-->
<!-- End trackback -->
Replace haloscan-id with your Haloscan login ID will do.
This blog has also enabled this feature as well :)
