Hi,
grasping is a harder skill than reaching... does your lo reach out to objects to feel them? i would find lots of bits and bobs that make noise, crinkly paper, keys, etc and things that feel different, velvety textures, cotton balls, etc and i would ensure that when your lo was on his back there are lots of things hanging overhead to bat and move... spend some time lying down with him and showing him how things move and running his hands accross some of the textures and noisy things you have found... you can probably place things into his hands because of the grasping reflex that babies have but i think that reaching is important first...
it might be that your ds is more interested in watching things right now, a mirror or even you. let us know how you get on!
HTH