I normally get familiarized with the niche before starting a project in it. I hang around at places where people from same niche mingle, see how the market is, what the potential is, how much traffic we can expect, what the crowd want etc.
Knowing the market always help. You can start with talking with peers in your groups. Understand what they expect from a project and then fuel it with the requirements. Some people want a platform, some want a store, some want referral links, some are interested in knowledgebase and so on.