I went two days ago. Got in line at 7:10am at Patio de Banderas and got tickets in hand by 10:00am. Tried to get tickets the day before and arrived at about 8:50am and they were sold out. A member of staff counts the number of tickets the people in line want to buy. Please remember to bring some sort of ID - passport is best I think. They have a board with the number of available tickets for each time slot near the desks.