Help:Introduction to the Manual of Style/1
The MoS
A vast resource
Article sections
Making articles readable
Images and refs
Enriching the text
Linking
Tying the encyclopedia together
Consistency
Final little things to think about
Summary
Review of what you've learned
The Manual of Style (MoS) is an in-depth guide that provides standards on how to format Wikipedia articles. Following these guidelines helps keep the encyclopedia clear, consistent and stable.
The simplest way to do this is just to find a well written article and copy its formatting. However, if you want more information on any formatting the MoS probably has a recommendation (you can search its contents here).
Remember, the MoS is only a guideline, you don't need to have the whole thing memorized! It's there to assist you setting out content when you aren't sure how to best display information and to stop protracted arguments if another editor disagrees.
Content is more important than formatting, and other editors can assist you if you're unsure (similarly, assume good faith when others help format your writing).