One of the most basic uses for contests and competitions is to increase your social page following. Ask people to like your page and perhaps also to tag 3-5 friends. If you want to grow your email list, require a sign-up form for all participants. Keep the form short and let participants know their privacy will be protected.
Before setting up the contest, have clear goals for what you hope to accomplish with it. The goal could be to gain a certain number of followers, to get so many sign-ups, to increase brand awareness or to hit a sales target. These goals will affect the type of contest you choose to run.
Your audience's interests are also a factor in the contest type. The generic “follow us and tag your friends to be entered in a random giveaway” is the most common way to gain followers and works for a wide range of target audiences. Email sign-ups may work better for an older audience that's less active on social media. Contests involving creativity such as photo contests or answering questions like “why do you want to win” increases engagement and helps you learn more about your audience. These tend to work better with younger target groups, and the prizes need to be attractive for them to be willing to put in the effort.
Make sure the prizes are something your audience will get excited about. If your product is new, you may want to give more away so that the lucky winners will help promote it. Collaborating with a related brand is a way to put together a bigger prize package on a small budget. Offer discount vouchers as consolation prizes to give potential customers an extra push to purchase.
Get people to join/follow and share
Set clear goals for your contest
Understand your audience's interests
Choose attractive prizes within your budget