Remember the human. When you communicate online, all you see is a computer screen. When talking to someone you might want to ask yourself "Would I say it to the person's face?" or "Would I get jumped if I said this to a buddy?"

Adhere to the same standards of behavior online that you follow in real life.

Read the rules of a community before making a submission. These are usually found in the sidebar.

Read the reddiquette. Read it again every once in a while. Reddiquette is a living, breathing, working document which may change over time as the community faces new problems in its growth.

Moderate based on quality, not opinion. Well written and interesting content can be worthwhile, even if you disagree with it.

Use proper grammar and spelling. Intelligent discourse requires a standard system of communication. Be open for gentle corrections.

Keep your submission titles factual and opinion free. If it is an outrageous topic, share your crazy outrage in the comment section.

Look for the original source of content, and submit that. Often, a blog will reference another blog, which references another, and so on with everyone displaying ads along the way. Dig through those references and submit a link to the creator, who actually deserves the traffic.

Post to the most appropriate community possible. Also, consider cross posting if the contents fits more communities.

Vote. If you think something contributes to conversation, upvote it. If you think it does not contribute to the subreddit it is posted in or is off-topic in a particular community, downvote it.

Search for duplicates before posting. Redundancy posts add nothing new to previous conversations. That said, sometimes bad timing, a bad title, or just plain bad luck can cause an interesting story to fail to get noticed. Feel free to post something again if you feel that the earlier posting didn't get the attention it deserved and you think you can do better.

Link to the direct version of a media file when the page it was found on doesn't add any value.

Link to canonical and persistent URLs where possible, not temporary pages that might disappear. In particular, use the "permalink" for blog entries, not the blog's index page.

Consider posting constructive criticism / an explanation when you downvote something, and do so carefully and tactfully.

Report any spam you find.

Browse the new submissions page and vote on it. Regard it, perhaps, as a public service.

Actually read an article before you vote on it (as opposed to just basing your vote on the title).

Feel free to post links to your own content (within reason). But if that's all you ever post, or it always seems to get voted down, take a good hard look in the mirror — you just might be a spammer. A widely used rule of thumb is the 9:1 ratio, i.e. only 1 out of every 10 of your submissions should be your own content.

Posts containing explicit material such as nudity, horrible injury etc, add NSFW (Not Safe For Work) for nudity, and tag. However, if something IS safe for work, but has a risqué title, tag as SFW (Safe for Work). Additionally, use your best judgement when adding these tags, in order for everything to go swimmingly.

State your reason for any editing of posts. Edited submissions are marked by an asterisk (*) at the end of the timestamp after three minutes. For example; a simple "Edit: spelling" will help explain. This avoids confusion when a post is edited after a conversation breaks off from it. If you have another thing to add to your original comment, say "Edit: And I also think..." or something along those lines.

Use an "Innocent until proven guilty" mentality. Unless there is obvious proof that a submission is fake, or is whoring karma, please don't say it is. It ruins the experience for not only you, but the millions of people that browse reddit every day.

Read over your submission for mistakes before submitting, especially the title of the submission. Comments and the content of self posts can be edited after being submitted, however, the title of a post can't be. Make sure the facts you provide are accurate to avoid any confusion down the line.

A client_id and client_secret can be generated for a reddit account by going to https://www.reddit.com/prefs/apps and creating an app:

The part I have hidden is my client_id.

Then you can use a client like praw to access reddit e.g. with Python:

import praw
r = praw.Reddit(client_id='insert id here',
                client_secret='insert secret here',
                user_agent='insert user agent')
page = r.subreddit('aww')
top_posts = page.hot(limit=None)
for post in top_posts:
    print(post.title, post.ups)

You could use your current browser's user agent, which can be easily found by google searching "what is my user agent" (among other ways).

I believe current policy is that the API app form is informative only (gives the reddit employees contact info in case they need to talk to you about your bot and can't reach you on reddit).

You can immediately start working with the client ID/secret you generate on the app creation page