(a) RSS More

Additional – you can use second time (for cut full article in full RSS).
Options available on Settings/Reading page

1. Upload a-rss-more directory to the /wp-content/plugins/ directory
2. Activate the plugin through the ‘Plugins’ menu in WordPress
3. If you theme is support ‘automatic-feed-links’ – all done

4. Another – add link to new RSS with param ?announce=1:

   <link rel="alternate" type="application/rss+xml" title="Blog » Announce Feed" href="http://domain.com/feed/?announce=1" />
   

   or

   <link rel="alternate" type="application/rss+xml" title="Blog » Announce Feed" href="http://domain.com/?feed=rss2&announce=1" />
   

1. 

   Settings on Admin page

2. 

   "Announce Feed" in browser

Are you sure? It’s best practice?

Yes, see on votes results http://habrahabr.ru/blogs/blogosphere/105394/ (it’s russian hi-tech community blog):

Question: Full RSS or announce only
1: Always full
2: When article don't consist some source code
3: Announce only

0.0.2

• Added options of plugin

0.0.1

• Initial version