Create a 3x3 mobile taming pen 3 walls high on a raft with a Dino gateway on one side and ramps on the other. Use a flyer to lead it up the ramp into the pen then move it to a safe area to tame. I got 2 150s without a single issue.
Feed it then mount. You won't be able to control it until the tame is done, dismounting appears to lower taming effectiveness so make sure you have a good supply of carrots (preferred food) on you. When it starts to buck you off you have to hit enter to feed it again. If you pay attention to the bottom left corner of your screen there will be a tool tip that will pop up when you can feed it abs just before it starts bucking.
Can kill squid like their kin in real life. Tame a 150 and you can take on alphas like they are regular ones. Just up health and memes. They recover steam so quick boosting it is pointless. An all around amazing creature, 10/10.
Never fight a wild giga with a tamed giga, a wild giga has 80,000 health and your tamed will usually be around 25,000 health. Also the wild giga will do more damage a bite and also has a health drain effect.