First of all, use good grammer. Do not use "u 2 4" and other things like that. Make sure your comment is about the post and it states an idea and is constructive. Also make sure your comment is not less than 100 characters. Maybe 100 characters is a lot but comments like "I agree" "Yes, it is a scam" "+1" are of bad quality.
Those examples are not examples of posts that are nonconstructive, but rather those that are of very low value and as such would be deleted by the forum moderation team (as those break the rules by default).
Also when your done writing your post look for red underlines and it will help correct most grammar and spelling mistakes people make.
This is good advice that I can agree with; the browser should be able to detect common spelling mistakes (it doesn't really work on grammar). Unfortunately, not too many people use this.
Just dont copy or repeat what others have already said.
Copying content will get you instantly permanently banned. You may be talking about 'rewriting' what others have said.
Do a through research before posting and last but not least be original,honest and speak your mind
Those three values are useless if you post on topics where your knowledge is either lacking or very flawed.
For the others that have mentioned it: The length of a post does not matter at all. Stop throwing in random trivial numbers and flooding this thread with bad advice.