Muscle memory and how to set it in your mind. Sorry if I missed a previous tips. Put your index finger down first, then middle and then ring. Get it as best you can. Actually talk to your brain and say "this is a C chord" go from variuos pressure and keep telling your brain this is a C chord. Play it as clearly as you can. Play it muted. All the while holding the C chord. I'd recommend doing an Am chord next as it has the index finger that stay place. Go through the same process of setting muscle memory.

Good luck..