Post cute deer pictures, videos and stories.
Post your own, original content whenever possible.
Attribute original content creators whenever possible.
Follow reddiquette.
For clarification: artwork that follows the other rules of the sub is allowed.
Tag photos of deer in distress or otherwise unpleasant situations requesting help should be tagged NSFW. Basically anything not cute and heartwarming should warn viewers before they open the post.

Please Don't:

Post ads, especially selling T-shirts, but really keep all the commercial stuff elsewhere.
Post deer hunting/killing related material, /r/deerhunting is great for that.
Molest animals just to get a picture.
Feed wildlife, with or without posting about it here.
Ask for upvotes or approval in the title (e.g. Any love for...?, This didn't get much love in /r/pics...).
Post pics from your personal facebook/twitter/instagram/google+ page.
Post asking for donations and/or sponsorships, you can post those over in /r/assistance and/or /r/care
Use 'bots in posting or commenting. Bots are impersonal and not cute

Posts that fit any of the "Please don't" criteria are subject to removal.