If your on a single player server or an unofficial server, I recommend getting two people, get on a rock, then start pelting rocks or tranqs in its head or upper body, I got 7 trikes in a few days doing this.
To tame one of those early game you just need to get yourself a slingshot (You can get the engram at Level 5), a low Level Trike (Level 1 - 30) and to be safe around 40 Stones. Then find some Trees and attack the Trike with your Slingshot then use a Hit and Run Technique. It should be much easier because the Trike gets stuck in the Trees and has to get around them. Which gives you enough time to shot him some times with your Slingshot. Once he is unconcious you just have to gather Berries. Use Mejoberries for a higher level after taming. Keep an eye on the Trike's Torpor(You find it in the bottom right hand corner in its Inventory). Once it drops on 0 your Trike will wake up and you have to knock it out again. To raise its Torpor you need to put Narcoberries in its Inventory, click on them and then click on the Remote use item Button (Each Narcoberry adds 8 Torpor). In the Dododex App you can Look how many Slingshot-Shots, Narcoberries and Mejoberries your Trike needs. Good Luck!