website for buying advance tickets to museums in Florence: link
Or call 055-294-883.
At the museum, walk past the long line to the special entrance for those with reservations, give your name and number, pay (cash only), and walk right in. It has been recommended that you call before 8:30 am EST to reach an English-speaking agent.
Accademia Museum (Tuesday - Sunday 9-7; Sunday 9-2) - home of Michelangelo's David, his unfinished Slaves (designed for the tomb of Michelangelo's patron, Pope Julius II), and the Florentine paintings from the 13th to the 18th centuries.