Here is some good advice about the headers for bulk emails, the likes of companies like constant contact use.
http://old.openspf.org/esps.html
To add to the list of good practices least likely to get you blacklisted,
If you follow guidelines for double-opt-in / unsubscribe links on every email / handling abuse reports this will improve the recipients not marking your email as spam - because if enough people within gmail/yahoo/hotmail mark your email as spam, it will go into the spam folder by default sometimes even if other good practices are being followed. So double-opt in makes sure the recipient only gets email they are expecting, reducing the chance of spam reports.
And to add to the managed email queue idea - do not just unintelligently process and send emails as fast as your CPU/memory will allow, create your own queue system as others have suggested that trickle over time and shuffle the order of email provider you are sending to (@gmail.com, @yahoo.com etc).