Like Richie said, just plant your cutting about 1-2 inches into Potting mix and leave them alone, just make sure they stay moist but not soaked. They do take awhile to root in good and begin new top growth but like he said, once they do there is no stopping them. Mine, purple flesh, were 8 inch cuttings 4-5 months ago and now they are a couple feet and some I have side branches which are big enough now that I can clip them and use it to start another. That's what I do anyways, instead of clipping it early I'm letting the first couple grow so I have a couple backups. Never know when something could happen to a plant. I also want to grow a yellow selenicereus megalanthus, badly but haven't found anyone to sale me cuttings for a reasonable price. Good luck growing yours!