So I just got my iPhone 5 a coupe days ago and I just can't seem to keep dust from getting inside my phones port and speaker holes and also the earpiece. I have a case on the phone but obviously it doesn't protect those areas. I also bought a can of canned air but that only works when I used it at that moment but as soon as I'm out the house dust starts getting in those areas. I also had this problem with my precious iPhone 4. Can someone help??
The only thing you can really do is get a case that protects the ports. Lifeproof, Otterbox (to a lesser degree) and Ballistic come to mind.
I carried a 4 and a 4S for quite some time with no case at all with few problems as a result of dust. Every once in a while, I would get a dust bunny in the headphone jack. Had to clean that out with a toothpick. Clean the dock connector with a clean dry toothbrush.
I have an Otterbox defender on my 5. Haven't had it long enough to swear to how well it will do as far as dust goes, but so far, so good. The re-designed speaker/mic grille should help some.