>>2851452It's not worth it to stop down much past f8, past that the diffraction will start to fuck away your sharpness. Also better to go a millimeter or two away from the extremes, it can make a big difference in overall sharpness and vignetting. I'm not sure how accurate exif reporting is but in my experience even 18.3-18.5 is noticeably better than 18 maxed out.
A circular polarizer can really go a long way, although it's a colossal pain in the dick with a rotating front element like most kit zooms have. On the plus side, since most kits have 52mm or similar filter diameters they're quite a bit cheaper than the 72 or 77mm of fancier glass.
