For a paid editor's talk-page declaration, see Talk:Mia Farrow.
The employer is whoever is paying you to be involved in the article (such as a PR company). The client is on whose behalf the payment is made (usually the subject of the article). If the employer and client are the same entity—that is, if Acme Corporation is paying you to write about Acme Corporation—the client parameter may be left empty. See {{connected contributor (paid)}} for more information. Note that other editors may add this template for you.
You are expected to maintain a clearly visible list on your user page of your paid contributions. If you propose changes to an affected article, you can use the {{request edit}} template. Post it on the talk page and make your suggestion underneath it. Paid editors must respect the volunteer nature of the project and keep discussions concise; see WP:PAYTALK.