What activity can I do to engage with my three month old baby?

For myself, I talk and sing to my LO. Do it together by engaging him by holding/ claping his hands, feet etc. Rattle some sound around to develop his listening skills. Also can train his motor skill holding onto various texture of materials like a rattle, soft toys, handkerchief and teether etc. I also put him on tummy time each day for about a few mins. I also read to him. Have fun with your babies=) Regardless of what you do...most importantly is to bond with your baby.