The University of Arizona provides a very good overview of how to negotiate.
At this point it's important to determine which rights you are interested in maintaining. Like any negotiation, it's important to define what matters to you.
Easiest of the two scenarios. You can engage in a back and forth with the publisher, striking out and adding language as needed. Refer once again to the University of Arizona guide.
If you are using an addendum, Science Commons provides this set of steps once you are ready to write back to the publisher with your requests:
(Source: Science Commons)
Still possible to negotiate but you will need to leave the manuscript system and liaise directly with the editor/publisher. In this case, you will attach an addendum to your email requesting whichever rights are most important to you. See section below for sample addendums.
For researchers who are subject to the Tri-Agency Open Access Policy on Publications, the Agency provides sample wording to include in the Addendum for authors who need to negotiate in order to comply with the policy:
[Journal] acknowledges that the researcher will be entitled to archive an electronic copy of the final, peer-reviewed manuscript for inclusion in McGill Library's eScholarship institutional repository. Manuscripts archived with eScholarship may be made freely available to the public, via the internet, within twelve months of the official date of final publication in the journal.
There are several organizations that provide templates for author addendums.
The Rights requested column outlines the particular set of rights this addendum by default advocates for; these are suggestions. The author may include/remove any particular language as they see fit.
Here's an example of how one researcher used modified addendums in their negotiations.
|SPARC author addendum (English, French)||
(i) reproduce the Article in any material form for non-commercial purposes
(ii) to perform the Article in public for non-commercial purposes
(iii) to convert the Article by preparing derivative works
(iv) to make a sound recording, cinematographic film or other contrivance by means of which the Article may be mechanically reproduced or performed for non-commercial purposes
(v) to reproduce, adapt and publicly present the Article as a cinematographic film for non-commercial purposes
(vi) to communicate the work to the public by telecommunication for non-commercial purposes
(vii) to authorize others to make any non-commercial use of the Article so long as Author receives credit as author and the journal in which the Article has been published is cited as the source of first publication of the Article. For example, Author may make and distribute copies in the course of teaching and research and may post the Article on personal or institutional Web sites and in other open access digital repositories
Additional commitments: Publisher agrees to provide to Author within 14 days of first publication and at no charge an electronic copy of the published Article in Adobe Acrobat Portable Document Format (PDF). The Security Settings for such copy shall be set to “No Security.”
Each addendum gives you
1. Access - Reuse:
You retain sufficient rights to grant to the reading public a Creative Commons Attribution Non Commercial license or similar license that allows the public to re-use or re-post your article so long as you are given credit as the author and so long as the reader's use is non-commercial.
2. Immediate Access:
You retain sufficient rights to post a copy of the published version of your article (usually in pdf form) online immediately to a site that does not charge for access to the article.
* Note these addendums include by default language that refers to the United States government.