Anyone who believes their copyright has been infringed must provide proof to ensure that infringement took place. A copy of the offending work should be obtained. This is very important as the other party may change their copy to avoid evidence of copyright infringement.
A copy of your work should also be produced with the sections you claim have been plagiarised highlighted.
If your work has been updated or modified since it was first registered then the original version should also be produced to compare with the offending copy. The date of registration should also be provided.
Any letters or other documents relating to your work should also be produced as well as any rough drafts.
All of this will help prove false claims by the copyright infringer that any similarities between the two works were purely a co-incidence.
Once the information has been gathered the infringer should be made aware of your concerns. He should be made aware of the work which was infringed and invited to make a suitable settlement.
The infringer should be given a suitable period of time to make his offer and told that legal advisers have been consulted.
If the copyright infringement occurred online the ISP and company in charge of network access should be informed.
If no settlement has been made within the stipulated period then a specialist copyright solicitor should be contacted.