The hardest fans to make are the first 10. The first people who aren't your friends but genuinely like your music because its good and they connect with it are the hardest but most important fans you will ever have. Due to this it is vital that you interact with them and make sure they now how must you appreciate them listening to your music.
Why are they so important?
Initially your band will grow fastest through recommendations by people to their friends. Whether it be by linking to your songs on Facebook or telling someone about you, people trust their friends opinions and are much more likely to listen to your songs if recommended.
If someone that you don't know interacts with your band in some way, get in touch with them. Say thanks, and build a relationship with them that will ensure they recommend you and come back to hear more of your music. Also use this opportunity to ask them how they found out about your band because knowing which of your websites/methods of promotion are actually working is vital information at this early stage.