For non-High School programs, there are 2 lotterys. One for Charters and one for public specialty programs (TAG, Language Immersion, etc).
Applications for the Charter one is usually in the late Fall and for the Specialty Programs in Dec or so.
If you are interested in a specific program, call when the lottery opens and ask if they are going to have a tour scheduled.
They usually announce the results after Spring Break. If you are on multiple waitlists in either lottery once you chose one you are kicked off the others.
There is usually a lot of movement in the lists over the course of the summer and they even offer seats in Sept if people drop out.