I am having some difficulty overwriting my subtheme code using my own theme.css file (located in sites>all>themes). I can find the code that results in the display of whichever css style property I'm trying to change (e.g., font-family in the header region) easily, using the chrome DevTool, but when I go to target that area in my own css file it seems not to have any effect on the display. Is there any general methodology with which I can go about inheriting my adjustments to the theme styles? FYI I have renamed my subtheme's files so that is not the issue.
Any help would be wonderful.