When taming, veggies wont work, so stand under its stomach and feed it mejoberries. When you stand under its belly, it will have trouble getting to you under there, so you don't have to worry about beong pushed off a cliff or into the ocean.
Grapple hook on to it. Hold to Reel yourself in, continuously feeding it while staying grappled. Rarely will hit you as it spins trying to reach you. Grapple wont releas because as long as you dont hit it, it wont count as combat