Ippier .... Yeah ... it's all about practice. Buy Guitar Scores and spend hours reading and playing ... but of course you must know your fundementals. Like Time Signatures, Quavers, Crochets, Tied Notes, and of course ... the notes itself.
There's a book from William Leavitt called "A modern method for Guitar" ... it's a Textbook used for Berklee school of Music. Can get it from D-Music ... Paradiz Centre. This is a book that teaches you to sight read on guitar ... it's good course it actually tells you how to position your fingers on certain notes on the staff.