Three Pillars of Wiki-Ethics
2Wikipedia's Conflict of Interest Guideline requires that you request corrections, propose content, and collaborate with the site's editors, rather than directly edit the page. This is in-line with how you would treat any other independent, autonomous website. In a nutshell, leave important content decisions to the site's editors.
3Wikipedia's Arbitration Committee (Wikipedia's Supreme Court) said marketing professionals are expected to comply with the spirit, as well as the letter, of Wikipedia's rules. This means avoiding advocacy, bias, or omissions. Make a good-faith effort to make the same contributions you would make if you had no connection to the topic.
How to Tell
Here's a shortcut to finding white-hat wiki firms. Use Wikipedia's list of firms it hasn't blocked. Firms listed under "Never Blocked" meet two basic requirements. First, Wikipedia knows they exist. Second, Wikipedia hasn't blocked them. Certainly, you should only hire a firm that meets those two criteria.
Have you noticed something? The full list on that page goes on for miles, but the "Never Blocked" section is just a paragraph. For various reasons, almost all Wikipedia firms are black-hat. Many firms falsely advertise they are ethical without disclosing they are banned from Wikipedia for using deceptive practices. Luckily, an army of Wikipedians have sorted them for you.
Schedule an initial consultation to discuss how the site's rules/norms apply to the page and the changes you're looking for.