Policies and guidelines
Why they exist
Content
Rules for writing articles
Conduct
Getting along with others
Summary
Review what you've learned
Writing on Wikipedia is highly collaborative. There are two good starting points for how to get along with other editors: be bold, and be civil.
When editing, be bold! Most edits make the encyclopedia better, and mistakes can always be reverted or corrected. If you see something that can be improved, improve it, and do not be overly concerned with breaking anything. If the change is in the spirit of improvement and makes sense to others, the odds are good that everything will turn out all right and the change will be kept. If not, it's easy for someone to change it back.
Being civil entails remaining polite and assuming good faith when interacting with others, and focusing on the content of edits rather than on personal issues. It requires participating in a respectful and considerate way, without ignoring the positions and conclusions of others. Assuming good faith means that we assume by default that other people's intentions are to improve the project. If criticism or moderation is needed, we discuss editors' actions but do not accuse them of harmful motives without clear evidence.
Editors typically reach consensus as a natural and inherent product of editing; generally, someone makes a change or addition to a page, then everyone who reads it has an opportunity to leave the page as it is or change it. Being reverted may feel a bit deflating, but do not take offense, as it is a common step in finding consensus. If you have a disagreement or suggestion, express it on the article's talk page, and politely discuss the change until a consensus can be reached. Never repeatedly undo another editor's edits; this is called edit warring and is disallowed. As a last resort, you can file a request for help resolving a dispute.