From Outwar Wiki
There are many quests in Diamond City which will reward you with experience and help you level up. To enter Diamond City simply click on the Explore button on the left of every page. You will want to look at the Quests page for a complete list of quests, their level requirements and their approximate locations. To view a list of quests you currently have active and your progress on them, click on Actions then Quest Log
When you start the game you will be in an area called the Training Grounds. The quests located in the Training Grounds are a good place to start and will eventually give you access to Diamond City. To start a quest click on the icon next to a mob's name and follow the instructions they give you. After completing the Training Grounds quests you should be at least level 10 which will unlock the first set of quests in Diamond City.
The best thing to use if you are lost is The Outwar map
This link right here will help you out on all of the training mission from Level 1-10+ 
Talk to barkeep Johnny in the Dusty glass tavern. He will ask you to get Five scorpion venoms for a new drink he is making. To get them kill the scorpions in the training grounds. When you get all five go back and talk to Johnny to get yet more exp.
By talking to the tavern regular of Dusty Glass Tavern you'll receive a mug to bring to the tavern regular of Chuggers bar. He will give you another mug to give to the regular at the Drunken clam. This regular will give you yet another mug to give to the regular at the Hard Iron Saloon. For the final step you will be asked to go back to the Dusty Glass to finish the quest. You will get exp through out this quest.
These are only a select few quests to get you started out there are MANY MANY more quests out there so explore and have fun! talk to all the mobs and creatures you can to get more quests. Quests don't always give you exp sometimes you get special items from them too! You can also pick up some cool stuff while dcing in diamond city to complete quests. Check your backpack often to see what you got. For a more complete list of quests check the quest pages that are divided up by level groups.
3. Joining a crew:
Crews are a group of players joined together to do raids, hit the hitlists, or just plain hangout. To join a crew click the crew button on your menu bar and go to invites. Pick the crew you want to join and click accept. When you are in the crew you chose You can attack the crew hitlist, attack crew-only mobs, or participate in crew wars. -There are Crew Adventures, these are raid mobs that you can only attack with members of your crew. Through these raids you can earn items for yourself, your crew members, or get items to sell on the trade block to get points to upgrade your crew. Items you earn from attacking these mobs are deposited into your special crew vault. Only the crew leader(s) or those given permissions by the leads are able to take the items out and give them to crew member(s). Crews also have their own independent point bank and forums. The crew point bank is only accessible by crew leader(s). These points can be used to buy upgrades for the crew or can be awarded to members. Points can be donated into the bank by any member in the crew. Crews also can get points by raiding Guardians through out Diamond City. -Crew hitlists are a list of players that the leads (or any players with hitlist permissons) in your crew that they would like the entire crew to hit. To access this hitlist click the crew button on your menu and go to hitlist. On the main page of this hitlist you can see how many hits have been made on a player. You can also click on the view hitter stats. on the top of the hitlist. This will show you who in your crew has made the most hits and stripped the most exp off the hitlist. -Crew forums are a way for all the members of a crew to keep in contact and for the leads to post important information that they would like all their members to know. there are many other features and advantages to being in a crew. Check it out and talk to your leads if you need more information. All crews are different and do different things in many ways.
You can trade non player bound items with another player by clicking on a link that is found on their profile.
You will be brought to a screen that has 3 boxes labeled: Your offer, "insert player name here"'s offer, and one containing all of your tradable items. There is also a set of instructions along the side. You will place items in your box and the other player will put items in their's. When you have both finished placing your items you may complete the transaction by pressing the accept button.
When using this function be sure to Never hit your accept button until the other player has already put their items up
You may only have one item transfer at a time so if you need to do so with someone else while you have one waiting then you will have to press the cancel button and reopen the trade again later.