Write properly, remembering the basic mechanics of writing.
Remember that your posts are viewable by everyone on these forums. The rules of grammar exist for one purpose: to allow people to understand what you are trying to say. If you ignore them, no one will be able to follow you without working really, really hard at it, and that tends to drive people away. In order to make your posts easy and enjoyable to read, use proper grammar, spelling, and punctuation.
Your discussion and help is important to the writer and others reading the story. If they cannot understand what you are discussing, you cannot be a help or an encourager to them.
Discussions, commentary and critiquing are privileges.
When providing someone with a critique, please help with a positive attitude. Do not post critique that is rude, offensive or hurtful. Make sure you are offering constructive advice, with the intent to help, not belittle or discourage the writer.
Please regard any commentary you get with an open mind. Those who take the time to read are an asset to you and your progress. Even though you are not obligated to implement everything posted, it is a good idea to at least respond to the poster's comments.
The first post in your commentary thread should include an introduction and links to your work for the person reading.
Do not use commentary threads as common conversation centers. That is what PMs (personal messenger) are for. Take all casual conversation to PM and leave the commentary thread for prose and poetry discussion.