I think you should talk to him/her a lot and also respond to her coos and babbling. Show her/him bright pictures, tell your baby stories, sing. I do all of these and also have a music box that sing different rhymes to him, trust me my 3months old son is really making me happy. It might not make a lot of sense now it gradually you'd see the results. There are also some baby apps I downloaded on Play store, you can check them out.