There are a lot of common mistakes that are made with drafts. Here are a few you must watch out for:
Writing about yourself or someone/something you're close to Whether it is yourself, a family member, a friend, an employer, a mentor/business partner, writing about topics close to you (and the people close to you) is discouraged as the article you will create may not be neutral.
Copy-pasting material You must write the article in your own words, or it may be deleted.
Not citing your sources Articles without independent reliable sources usually get deleted within days.
Overly promotional language Terms like "leading expert" and "ground-breaking technology" sound great when promoting a product, but they do not belong on Wikipedia. Let the facts speak for themselves.