There are two entrances to the Acropolis: the west entrance is the main one, and the side entrance (known as Dionysus Theater entrance), which is located in the southeast.
If you use the main one, you should know that it is usually very crowded. You should be prepared to wait long in the line to enter the site.
We, at the Athens Walking Tours, use only the Dionysus Theater entrance for all the advantages it offers us: