You can do best if you keep these few points in your mind before making post.
Take a paper and write a topic on it first.
Write main points of your topic.
Think deeply on the points for details.
Compare your topic with other people's thoughts.
Try to use easy wording to give a good message.
Select images related to your topic even single.
You should avoid extra details which causes boring to the reader.
Always give a good message to the reader.
You can also use proverbs in your explanation in quoted.
Never think that you are late in posting but think that you are making unique and valuable post.

Very good initiative you have taken .All these points you have mentioned above are much supportive for writing quality content.
This contest will surely highlight quality content writers .