there are frequency charts online that are a nice guide and a great place to start your eq settings at for certain sounds, but like everyone said, every sound is different... you need to use your ears and some basic filter/eq knowledge...
and like formant said, find out what frequencys is bugging you for general eq purposes. grab your parametric eq, and adjust the q on on of the bands , give it a big boost, and move it around. boost the q to make it more 'narrow', lower it to make the curve wider...
obviously for finetuning frequencies you need a narrow band, so adjust it and then move it around slowly, certain sounds will jump out at you... thats how you can see what some of the dominating and lackign frequencies are...
for sidechaining purposes ill usually use a dedicated channel with nothin but maybe a hihat to trigger the destination compresor/gate... or if you want to use the signal to sidechain itself then yeah, use basic filter knowledge to get the sound you want out of there...
obviously if you just want to compress using the bass of the signal you use a low pass filter, if you want to use mids use a band pass, you want to use the highs use a high pass...