Contest rules?

Contest rules?

I know I dont post much, and I have never completed one of my projects, never sure where all of my time goes, however I was wondering what are the rules with regard to contests.

I only ask as I have an idea for one, mostly inspired from various bits of news I have stubbled across and on of current obsessions/half finished sketches.

I dont have any prizes, it would be bragging rights only.

I am thinking of making it very narrowly focused, which i thought would be interesting.

What do people think?