Shoot him with tranqs as soon as he wakes up at night,its best that way if youre taming a high lvl one,that way you only need to put him down twice. Starve it depending on the food youre feeding it, cause if you feed him and he wakes up (20:30)you lose all taming progress. So starve him,the second time it wakes up and you tranq him he will have enough hunger to eat all of the kibble at once and tames in 1 min. The caves are dangerous so bring a friend and the best cave for finding him is the Grave of Tyrants in Schorched Earth. Google the rest.
Useful tip for everyone: Ark’s day and night cycle is 1 hour in real life (on normal settings).
That means if you shoot the dinosaur right out at 8:30 p.m., it will wake up in real time in one hour at 8:30 p.m. the next day. For each past hour you have to subtract 2 minutes and 30 seconds. Example: you knocked him out at 10:30 p.m. -> he will wake up in 60 minutes - 2,5 - 2,5 = 55 minutes
At level 26, it is the first time that the Megalosaurus needs more than an hour to be tamed.. So be prepared to knock him out twice or three times