If you can get the women to come out and hang out during rush, that's all you really need. Freshmen want to go where they're going to meet women!
Obviously, if you have nice facilities, esp. outdoor ones, milk them for all they are worth. Some burgers on the grill, a pickup volleyball game, and some music will suck in a lot of passers-by. And the only real cost for an event like that is the food.
The fraternities on my campus that were the most successful fell into two camps: Those with lucky locations and a nice porch who got the freshmen, and those who excelled throughout the year (did well in Greek Week, had high grades, elected a homecoming king) and attracted men by knowing them from classes and the dorms.