you want your lights on for 12hr then off for 12hrs. mine come on at 9:30am then go off at 9:30pm. i reccomend a simple two outlet digital timer, can be puchased at wallmart or homedepot for less than $20.
I do the same. But I do 11on/13off in the winter and the reverse in the summer. Spring and fall are 12/12. I don't know if it really matters to do that but I try to recreate natural environment as much as I can.
Now is the best time to get timers because all the christmas light timers are on sale! Those work perfectly for me and they're like $2 at walgreens/CVS.