Points

Are there any contest going on to improve the earning system?

Do not start a new post for this. Ask the same in queries post which already exist.
Answering to your question, member of the week, revenue sharing, top voter of the day, Top writers contests are on.

On your dashboard there is clearly written in which section you earn points and in which you can earn money and if have doubts then three is a section on dashboard 'Read Me' Just go through it....

All the systems are best answered in FAQs so no repeat to post in forums.