Not really. I avoid stuff if I see it, but I don't specifically look out for it. Apart from big patches of broken glass or hunks of metal, I haven't really swerved to avoid puncture hazards. The stuff I have gotten flats on (very few) I never would have been able to see:
1) a T50 staple
2) a tiny sliver of glass (BB sized)
3) a very small piece of steel wire, about 1/2" long, probably 28 gauge, rusty.
That's the extent of my flats since I started commuting, a total of about 4000 miles so far.