Put the "pups" in pure sand (or sand amended with just a minor amount of compost). Just nestle the "bulb" into the sand a bit -- dont' bury it completely. Then set it aside in and come back in a couple of months. (I mean that literally. ignore it. Don't even water it. Just let it have whatever rain falls.) Should be rooted in a couple of months. Putting it in water guarantees it will rot. Sagos are one of those plants they say "thrives on neglect".