Shanks, for one, is the first character we see in One Piece. He appears in Chapter 1, as a pirate anchored at Luffy's town. He and his crew stay there for a month, and within that time frame, Monkey D. Luffy (the leader of the future Straw Hats, and the main emphasis of One Piece), looks up to him. Luffy wishes to join his crew and carves himself with a knife to show his bravery (that's why he has a scar). Of course, he is too young to be accepted into such a dangerous life. One day, as Shanks and Luffy are sitting in the bar, Higuma, a man worth 8,000,000 berries, tries to attack Shanks. Of course, Shanks does not feel like dealing with him, but Luffy feels offended that he insulted Shanks. Later on, Luffy finds himself in a fight with Higuma (after Luffy swallows the Devil Fruit that Shanks brings), and Shanks comes to the rescue. Shanks deals with him, but Higuma escapes and throws Luffy in the sea, and since Luffy can't swim, Shanks comes to save him. Sadly, a shark comes to attack and bites Shanks left arm off, leaving Luffy feeling guilty. Shanks later disembarks, leaving Luffy with his straw hat, telling him to see him on the Grand Line as a great pirate. Hence, sets off Luffy at age 17 as a pirate :D!

  After shanks disembarks Luffy's town, he goes to the Grand Line, and we never hear of him until several chapters later. We catch a glimpse of Shanks as he sees Luffy's bounty which Mihawk presents to him (which he rejoices over). Then, after Crocodile is beaten, Shanks is up next in line to take his placea as one of the Seven Sea Knights, in which he has to fight it over with the white beard pirates, which is where we see him last (visiting them). We currently don't know Shanks' bounty.