Complete 50 optional quests.Important notes:
-Difficult to track as there are no in-game tracker as to how much optional quest you've completed.
-You CAN repeat the same optional quest.
-There are well over 50 different optional quests if you don't feel like grinding the same quests over and over.How to get this achievement quickly:
I paired this achievement with Capture Pro (Capture 50 monsters).
1. Get to the quest board and under the Optional category, select the level 2 stars quest: "Snatch the Snatcher' where you need to capture a low-rank Kulu-Ya-Ku. (If you have unlocked this quest, try to talk to the Smart Biologist in Astera.
2. Start the quest and if you are high rank you don't need to eat or anything, I suggest bringing/crafting your own Shock Trap in order to always have 2 on you (When starting the quest, you can find 1 Shock Trap and 8 Tranq Bomb in the blue chest).
3. Follow the flies or track the Kulu-Ya-Ku (when you have a general idea where he is, you can always just run to the same spot as he will always spawn in the same place).
4. Weaken the monster but be careful, you are on a low rank quest and you will kill him quickly. For me a dual blade player, 3 combo was enough for a capture and 5 combo would kill him and fail the quest.
5. Once it's almost dead and you can see the skull on the minimap, drop the Shock Trap in front of it and use 2 Tranq Bomb. Voilà, you have completed an optional quest and a capture! (My average completion time was 1min45sec to 3min)
6. Select the option to go back to camp so you can save yourself some loading time. Once you are back at the camp, speak with the handler and accept the same quest.
7. Repeat step 1-6 to get both The Hunter's Life for Me and Capture Pro
Enjoy and if you have any questions, don't hesitate