score:2
There are several suggestions to choose from:
Buy the Alhambra card which includes a ticket to enter the Alhambra on the day.
Book a guided tour, there are almost always tickets online.
Get up early, if you want to wait in the line get there early as some tickets are sold on the day
Visit the free parts of the place that can be entered without a ticket
More suggestions/details can be viewed in this guide.