If you need help, first try the font identifier. At the end of the process if the results are bad you will find a link that lets you post the image to the forum so other users can help you.

A picture from AVICII twitter Font sample uploaded by TheWhiteUnicorn to identify the typeface on WhatFontIs
Worth paying attention to "L" upper loop Font sample uploaded by TheWhiteUnicorn to identify the typeface on WhatFontIs

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