Taming one is simple: Stay under him behind his front legs so he cant reach and push you out and start feeding him, he will eventually stop moving. While feeding it tell your friends to stay away or it will start moving again.
It will take some time until he asks for food for The second time. After that its easy, just give him The best food you can to make it faster.
These are naturally peace-loving creatures, preferring to spend the days grazing about the island’s many hills and valleys. They have an inherently playful nature, leaving them undeterred by any predators until they become severely injured, at which point they get scared and will attempt to flee. Because of this, tamers have taken advantage of this overtly trusting nature and have tamed it like so. They have also tried to jump on it’s back for taming, usually just to find themselves tumbling back down to the ground again. The Diplodocus is so trusting that one can even knock one unconscious for an easier tame, at the cost of tranquilizer arrows, and a fair bit of them. Also, be careful during the taming process as they tend to nuzzle you in an act of affection during so, and be careful if traveling near a Diplodocus who is unaware of your presence with a berry-gathering animal, because it will gladly take an accidental hit during gathering as a play-invitation.