Running a contest is one of the effective ways to increase number of followers in social media. However, there are things to consider in doing this.
First, you need to determine the limit of contestants who can join. You can use the geographic and age limitation for this matter. It is also important to note how the winner is determined and voting is not a way to do that. You also need to set requirements for contestants.
Also, give a reasonable prize and make sure that they are not too high for the contest. Lastly, make it a great experience for the contestants.
Source: Ad Week