What to use to keep flies away during outside parties?

http://makinglemonadeblog.com/how-to-keep-flies-away-fly-repellent-water-baggies/

a slice of watermelon on a plate far away from you...

Have all your guests wear spider costumes !

Fans work well, if they are correctly positioned. But here is a no-fail: I'm from the Bayous of New Orleans. Flies are everywhere. And gross. Fill a ziploc bag with water and drop a shiny penny in it. Hang them up where your guests will be gathering. For a porch, you could just use a large cup screw and and one of those office clips. Put the clip on the bag, then hang the handle thingies on the cup hook. Doesn't look great, but it works...just make it a conversation piece. Depending on the size of your party, you may need to do a number of these. Flies have faceted eyes, and it's something about the way the "see" the penny in the water is troublesome to them...they fly away.

Hope this helps.

Durina, I haven't tried it but I've read that wiping all surfaces with Pine Sol will work well.