First, join the Brotherhood Of Steel, which can be done immediately after the game starts. You can join by going to Cambridge Police Station or just following the main story. Either way triggers the "Reveille" and "Fire Support" quests. Follow the Brotherhood's quest line until they make you a member. Then, complete their "Tour Of Duty" quest, where you will meet everyone on the airship. Next, make sure to have a high-damage Sniper Rifle with a long-range scope (should be 50+ damage, which can be bought from vendors in Diamond City or Bunker Hill). After joining the Brotherhood Of Steel, travel to Prydwen (their airship headquarters), and talk to Proctor Quinlan. Choose to assist on a patrol, and he will give you the "Learning Curve" quest. After activating the quest, go to the deck of the airship. Make sure to set the difficulty to Very Easy. Instead of doing the quest the normal way, you can shoot the Brotherhood ally you are supposed to protect right from the airship, and it will end the quest. He dies with 1-4 headshots on the Very Easy difficulty. After killing your ally, the quest immediately ends, but you still get to keep the reward for the quest. Make sure you crouch and are "hidden" before firing a shot and remain hidden before taking a single step or the guards will kill you since you have just killed one of their members below. Then, return to the quest giver for your XP. He will give you the exact same quest again. Repeat this as many times as desired. Each run takes approximately 90 seconds with loading times if you can kill the target in one hit (use strong .50 caliber sniper rifle). If your Intelligence level is at 11, you will get approximately 419 XP for completing the quest, plus 42XP for killing the target. That is 461 XP in 90 seconds or 3,073 XP in 10 minutes if all goes smoothly. Even with less Intelligence, you can still easily score around 2,500 XP in 10 minutes. Use this method to quickly reach Level 50 and get the "Legend Of The Wastes" trophy.