You can't directly reduce revolt risk (except through certain cultural techs that reduce revolt risk by 1, forgot which line of those they are), but militancy is the main causer of revolt grief.
Having a party in power that coincides with most of your population's ideological beliefs, social reforms (regardless of how funded they are) and plurality (high if you are democracy, as close to 0 as possible as a dictatorship) and low taxes all help reducing militancy a good deal. Stationing soldiers in a province will also reduce the militancy growth in the given province by .2.
However, if you recently added to your nation a province that is not a core and has non-national pops, then you're bound to get revolt risk in those provinces in the next ten years, even if their militancy is zero - the more non-national pops in absolute terms there are, the higher the risk will be (which is why it is utterly painful to annex China, British India, Japan, etc.)