I just wanted to provide more clarification on this.
1. Filter for junk leads according to filters that you declare are important. This is in reference to the article above (
http://community.marketo.com/MarketoArticle?id=kA050000000KytICAS ). Some of the common filters I see marketers use are:
- Email Bounced
- Email Invalid
- Not Data Value Changed (for a specific data value that you declare is important to you, such as Lead Score)
- Lack of Activity (in conjunction with other filters such as Not Opened Email, Not Clicked Link in Email, Not Visited Web Page)
2. Duplicates - Merge duplicate leads:
http://community.marketo.com/MarketoArticle?id=kA050000000KytMCAS