Hey I have a 96 civic LX with a automatic transmission.
when I drive for a while, my idle sometimes drops down to around 3000 and shakes mroe when i'm on D
when I Put it on neautral it raise up a little and stops shaking.
Would adjusting the idle set screw work?
I was reading around and would cleaning out IACV help smooth out my idle? If so how would i do so?

 

you can adjust the idle screw and most likely it will work, but that's the short cut.
clean out you TB, when was the ast time you replaced the fuel filter and air filter.

 

heres how to clean out your IACV: https://honda-tech.com/forums/acura-integra-6/%2A%2A%2Ahow-clean%2A%2A%2A-your-iacv-k-idle-air-control-valve-1575913/ but i would recommed doing what philosofy1 sayed too

 

If you are driving and the engine rpm is over 3000, then you are having more than idle problems. If your rpm drops down to 3000, then something is cutting out, fuel or some sensor is telling the ECU to drop the rpm. Get a reading out of the OBDII reader.

The idle adjusting screw only works at idle (no pressure on gas pedal). Same with the IACV.