Short answer
Create an account, check the subject has significant coverage in independent reliable sources, write a neutral draft with a citation for every claim, and submit it for review. Most pages fail on the second step, not the writing. Without independent coverage, a well written page is still deleted.
Start with the sources, not the draft
Wikipedia does not ask whether a person or company is important. It asks whether independent publications have already written about them in depth. That is called notability, and it is the single reason most new pages are declined or deleted.
Coverage that counts is significant, published by a reliable source, and independent of the subject. A feature or profile in a recognised newspaper or magazine counts. A passing mention in a list does not.
Coverage that does not count includes your own website, press releases, interviews where you do the talking, columns you wrote yourself, social media posts and announcements of a job or a campaign. If this is most of what exists, the page is not ready, and writing it faster will not help.
How many sources is enough
There is no magic number, but reviewers look for several separate, in-depth pieces from different publications. One strong profile is rarely enough on its own. Three or more independent articles that each cover the subject properly is a more realistic starting point.
Count them honestly before you begin. Many people discover at this stage that they have two good sources and a pile of material that will not be accepted.
The account and the draft
You need a registered Wikipedia account. New accounts generally cannot publish a new article straight away, so new pages go through Articles for Creation: you write in a draft space and submit it for review by experienced volunteers.
The review can take weeks, sometimes months, and a first decline is common. A decline tells you what to fix, and you can resubmit.
How to write it so it survives review
Write in a neutral, plain tone. State facts and attribute them. Remove adjectives such as leading, renowned or award winning unless a source says exactly that and you are quoting it.
Put a citation on every claim that a reader could doubt, and make every citation an independent source. A page that reads like a brochure is deleted even when the person is genuinely notable. That is the most common reason a deserving subject loses its page.
The rule people skip: conflict of interest
If you are the subject, work for the subject, or are being paid to write about them, Wikipedia calls that a conflict of interest, and paid editing has to be disclosed. Undisclosed paid editing is a policy violation, and it is how pages and accounts get removed.
The next guide covers what you can and cannot do if the page is about you.
When it is not worth trying yet
If the independent coverage is thin, the honest answer is to build it first. A page can be declined, deleted and later harder to recreate. Waiting until the sources exist is cheaper than a failed attempt.
In the meantime a page on a site with a lower bar for inclusion can give you a neutral, cited profile. The third guide in this set compares that option with Wikipedia.