When I teach sweater knitting I spend a lot of time emphasising the importance not just of swatching, but of swatching in the same way that the garment will be knit. One of the most surprising things that can make a big difference to gauge is material or even the brand of the needles. This blog post from designer Alex Winslow is a wonderful illustration of just how important it is to swatch with the exact needles that will be used for the garment. If you're struggling to match gauge, on the other hand, try switching up the kind of needles you're using.
Needles are one of the things I'm fussiest about. I really only use slick metal circulars, Addi Turbos or ChiaGoo Reds, and occasionally long metal dpns with a knitting belt. Anything else is too flexible, too lightweight, or makes my teeth feel funny (Addi Lace, yeah... odd). Bex just reminded me about the new(ish) pointy Addis that aren't strangely coated — must try those! One of the few times being irrationally picky makes life simpler — I don't need to worry about this issue very much! Have you noticed a difference in your gauge or knitting style with different needles? Or are you as fussy about needle material as I am?