Apart for a dead quiet signal chain, using really good quality cables such as van damme, sepearate mains adapters, recording in a faraday cage
one of the easiest ways to get really excellent detail to your recordings is to record at a sample rate least 48kHz and a bit depth of 24bit.
Sample rate is just howmany slices of the sound it takes in 48kHz means it takes 48,000 slices, 44.1 means 44100, so you get nearly 10% improvement in resolution...
44.1khz is the standard, but it doesn't mean it's YOUR standard, you'll get a much finer resolution in your recordings, which can be reduced by dithering down to 44.1.
Try it, it really does make a difference, but you computer needs to be pretty beefy and have a good sized RAM (I use 48gb)
Good luck...