Many people approach Wikipedia as a noticeboard onto which to pin something about their company, band, group or client. What they want to post could be described as a manifesto - it describes its subject but is also designed to stress its virtues and advantages, to tell the world how good and useful it is. It is very likely a copy of a website or Facebook page.
This is a mistake. Wikipedia is an encyclopedia, which is something quite different. One important difference is the tone: a manifesto is often written in the first person and uses PR-speak, promotional language and peacock terms, but an encyclopedia article requires a neutral point of view. A manifesto is designed to promote, but Wikipedia is specifically not for promotion of any kind.
Another difference is that you will not own any article you put in - see WP:Ownership of articles - others can and will edit it, you will not be able to insist on your preferred version, and you may fall foul of Wikipedia's Law of Unintended Consequences.
Wikipedia has three key content policies:
- WP:Verifiability - it's not whether you think it's true, or know it's true; it's whether you can cite a reliable source for it
- WP:No original research - this is not a place for first publication of new ideas, or even new conclusions from old ideas
- WP:Neutral point of view - we are not here to promote anything, even noble causes
There is also an important guideline used to decide what articles shall be included:
- WP:Notability, which is not a matter of opinion but must be demonstrated by showing "significant coverage in reliable sources that are independent of the subject." The test is, have other people, independent of the subject, thought it important and significant enough to write about?
It is preferred that users writing about a subject are not closely involved with it. Close involvement obviously gives them personal knowledge, but the No original research policy means that contributions should not be based only on personal knowledge; and experience shows that people closely involved with a subject find it very hard to write about it in a neutral way. The problem is that their interest, to present the best view of their subject and expound its virtues, conflicts with Wikipedia's interest in a neutral view. This situation is known as a WP:Conflict of interest.
It is impossible to prevent people with a conflict of interest from editing, but a code of practice has been worked out which helps to avoid the dangers: see Wikipedia:Plain and simple conflict of interest guide. The basic idea is that rather than make directly any but the most uncontroversial changes, you should propose them and let other, uninvolved editors decide. ("Editor" means the same as "user" - there is no separate class of "editors".)
There is excellent advice for editors in this situation, which addresses both the COI issue and any doubts about notability, at User:Uncle G/On notability#Writing about subjects close to you:
When writing about subjects that are close to you, don't use your own personal knowledge of the subject, and don't cite yourself, your web site, or the subject's web site. Instead, use what is written about the subject by other people, independently, as your sources. Cite those sources in your very first edit. If you don't have such sources, don't write.
It may then be possible to add material based on primary sources, but if an article cannot be written on the basis described, there must be serious doubts about notability.
If you do decide to write about a subject where you have a COI, take great care to avoid anything that seems like promotion. Remember the verifiability policy and, whenever you are about to write a glowing adjective, or indeed any claim, imagine a hostile critic looking over your shoulder saying: "Who says so? Can you prove it?" Put right out of your mind any idea that you are writing for your subject, because that is the quickest way to speedy deletion as an advertisement. You should be writing for Wikipedia about your subject from outside - a neutral description, plain facts cited to reliable sources. Write what a general encyclopedia reader might want to know, not the story the subject wants to tell them.
Your user page is not a place for promotion, either: although user sub-pages may be used for development of draft articles, main user pages are for the individual volunteers who are here to build an encyclopedia to say a little about themselves, if they choose, to help communication within the project. They are not for substantial content unrelated to Wikipedia.