When and how should I edit questions and answers?

Question

From the first day on I can edit other peoples questions and answers.

What is a good edit? Why and when should I do it?

Answer 1

Edit questions that are on topic here and not duplicates.
Edit answers that are answers.
Flag the rest or vote it down.

Fix all problems in one edit. If you edit the title, make sure the post body and the tags are fine too.

Don't be shy. At least 10 of our top reputation users are not native English speakers. Your help is always welcome.

Title

Start with the title. 90% of our visitors come from search engines. They see the title first. Let them know we have a question here that fits their need.

The title should be the question in a very compressed form. It should be a complete sentence without any error. A trailing question mark is almost always required.

The title should not just repeat the tags.

Remove the words help, problem, question and WordPress.

• How do I write a good title?
• Would the Stack Exchange network be better if titles contained complete, grammatical questions?

Post content

• Fix the spelling.
• Remove noise: Hello, Thanks, multiple exclamation marks, SHOUTING, anything which isn't a necessary part of the question.
• Fix formatting: Overly long code which produces scrollbars, missing paragraphs (line breaks).
• New users cannot insert images, they use a link usually. Insert that image if it helps to understand the post.
• Make sure the question stands out and is understandable.
• Some questions are so vague, we cannot tell if they are on topic. Narrow those questions down until they are on topic.

See also: Should I remove this from a post or title?

Tags

The first tag will be set before the title. Again: Think about search engines. Make sure the first tag is the most significant.

Remove noisy tags. Avoid tags that are too similar. Those are merge candidates.

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Review your edit: Is it complete? If the reviewer has to improve it you don't get the reward and your name will not show up.

Edit message

Describe what you did. Make sure it is as good as your edit.

I have seen this message far too often:

Fixed grammer

Uhm … no.

Make sure your edit is not too minor. We will reject very small edits.

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When you're done: Don't forget to vote! If the post was worth your time – vote for it.

Reputation

You earn +2 reputation for each accepted edit – until you hit 1000 wall. But, please, don't stop editing then. :)

Users with 500 reputation can retag questions without review, 2000 is the limit for editing questions and answers without review.