Don’t Disavow Links to Old Content
You don’t need to disavow links for old content which is no longer on the site, you should only do it for links from low quality sites.
Disavow On the New Domain After a Migration
When you migrate a website to a new domain, you only need a disavow on the new domain.
You Don’t Need to Remove Links If Asked
If someone asks you to remove a link to them, you can just ignore them. They can disavow you if they want, which won’t harm your site.
Disavow Backlinks on New and Migrating Domains
If you migrate a site to a new domain which has unnatural backlinks, you should disavow the unnatural links on the new domain as well.
Reconsideration Requests Don’t Work for Algorithmic Penalties
Reconsideration requests can’t be made for algorithmic penalties like Panda and Penguin. You need to do is disavow the links, or fix the quality issues for the penalty to be lifted in time.
Monitor and Disavow Backlinks Regularly
It’s good to monitor your new backlinks links for potentially low quality, irrelevant links, and disavow them, to avoid any risks from backlink penalties.
Disavow Works Immediately to Prevent New Penalties
A disavow link submission file is processed as soon as you submit it, and the link will effectively be nofollowed or blocked the next time the the link is crawled, so this will prevent a new penalty.
Backlink Disavow Doesn’t Do Anything Until Google Updates Penguin Data
If you have a Penguin penalty for backlinks, and you remove or disavow those backlinks, you won’t see any effect until Google updates the algorithm again and refreshes the data. John says it’s a long delay and you should go as far as possible with disavow including domain level disallow directive to make sure you cover as much as you can.