Sources showing notability, and whether they meet Wikipedia's general inclusion criteria, will be examined here. Some topics have specific topic guidelines, which are listed below under "Subject-specific guidelines".
To show notability, you should list the key evidence of reputable journals, independently published books, reputable news and media sources, widely reputed measures of recognition, and other reliable independent published sources, which show significant attention being paid by those independent sources to the subject of the proposed article. These are crucial and must be available to support an article, as it is a measure of how much the wider unconnected world has shown significant and likely enduring attention.
Wikipedia is an encyclopedia and is selective. Material that isn't "encyclopedic" (not suitable for an encyclopedia) or is "indiscriminate" (non-selective/arbitrary material), may have a problem.
Wikipedia considers enduring notability. Material that is routine may have a problem. Being "big in the news" or having many references doesn't change this (many things get attention for a brief period but are "just ordinary news"). Events and news material need to be quite significant to be covered.
Articles on living people have especially strict rules because it's easy to do harm. Sources must be very high quality, people noted for one event usually get covered in an article on the event not an article on the person, and borderline cases are much more likely to be deleted (especially for minors or where the person is notable for negative reasons). However if they are genuinely agreed notable then the biography will be included and neutral regardless of whether positive or negative.
The acid test is that people who genuinely are uninfluenced by and independent of the subject have decided that it is significant enough to write substantially about, and credible reliable publications feel it is of wide enough interest to write about it too. This could also mean that the subject was chosen over many alternatives or has gained unusually clear recognition such as a major award or position. That interest is what notability is actually trying to assess, not just the fact of coverage itself.
Self promotion and routine coverage do not create notability. The test is coverage of a kind that shows actual wider interest by credible published sources, not paid placements, nor the kind of occasional, routine or local coverage that any business or person might get now and then, nor minor and little-recognized awards, nor mere search engine "hits", nor "hearsay" or anecdotal evidence.
Notability can set quite a high bar. For example local politicians, most professors, most bands and websites, many schools, most crimes (including violent and widely reported crimes) and most matters in the news (even widely reported and circulated) are "just routine"—most politicians are not especially notable, nor are most schools or companies, most crimes or events. Likewise, minutiae and topics only relevant within a narrow-focus group or community with little or no wider notice or relevance are often not considered notable.
Notability is not inherited. For example having famous relatives or clients or being the creator of a well-known item or an item that was created by a well-known entity does not confer notability. The subject of an article must be shown to be notable in its own right, not just due to "reflected light" from others.
Subjects noted only for merely filling a role, where the role and not the subject was what really got 'noticed' (i.e. any person or entity that filled that role would have had the same coverage). In many cases the subject fills the role by pure chance or incidentally (bystander witnesses, selected spokesperson, interviewed participant, etc) and gets coverage in that role. Happening to be the occupier of that role won't of itself evidence the subject's notability. Note - some kinds of role may well show notice being taken of the person (CEO, cabinet secretary/minister, etc).
Articles exist because evidence shows the world at large deems the subject worthy of notice (as described), not just because it is interesting, useful, liked/disliked, some people may want to know about it, etc.
The person who created it or their motive is not a deciding factor.
Being badly written isn't a factor, we can fix poor writing if actual sources exist. (But actual lack of adequate sources would be a problem.)
Other common inquiries related to article viability
If you want to edit about yourself, or organizations, products, people, or matters having a close personal connection to you, or if you wish to engage in paid editing, you must read the Conflict of interest guideline, and you are urged to ask on this page whether the article is viable before creating it.
Additional notes:
For possible non-notability, you should review and summarize the available sources, showing why you feel the criteria are not met.
Detailed contents of articles and their quality of writing is not discussed here, and opinions expressed here do not guarantee an article will be kept on Wikipedia (ie, editor feedback and not a formal decision).