The lights are on
If you want to know an easy way to level up your character in the game, Dead Island, you have come to the right place. Although this may take some time and money, it is one of the quickest ways to level up in Dead Island.
In the Second Act, you come to a church, after doing some quests for the Church, a man named "Bruno" will talk to you. Bruno is located next to the workbench and can be heard asking for help at St. Christopher's Church, which has been converted into a safe house, in the quest Fortress of God. After completing the Fortress of God quest, Bruno will now offer you a new quest titled "Three Nails". You trade 3 nails in for $140 and 500 XP. This has not been lessened by the developers yet, as of 4 March 2012.
The easiest way to get these nails is to buy them every time you go to a vendor who has them, or continually go to different vendors until one of these vendors has them. You will want to keep a lot of money on you so you can buy as much as possible. Some people say that if you carry to many items with you at once you may glitch. But, I have carried at least 400 items around with me and did not have a lock-up/glitch.
Good luck and happy hunting.