Ez tame even for early game , just use 4 billboards, put around rhino when still unaggro and then when the rhino is trapped with the billaboards just start shooting tranqs . ( Can use wooden billaboards)
If you want to tame a rhino make sure the area is clear if it's not clear kill the direwolfs or other wild dinosaur and stay up hill so Rhino can't get you and use Shocking Tranquilizer Dart it takes to 3 shots and hes or she down.
When KOing just run in circles filling it with tranq arrows or darts(high level) this is the way to cheese this Dino’s taming. Even someone that just got into a world with good movement speed could do it easy. And the Dino’s are super op when fully charged. This will help ALOT :)
Use an argy trap! I was able to tame 2 lvl 150s with one. 4 stone gateways placed in a row with gates at either end once you have got the rhino in. Make sure you have a beast to protect it in case of things like rexes and sabers while its knocked out. They're so easy to tame and are absolutely brilliant once tamed.