Another good thing to try is to reduce the pressure you use with your left-hand fingers. If one finger is pressing down too hard, it can cause another to lift too far from the fretboard when you release it. Try fretting a note and then picking it. Then keep reducing the pressure you're using to fret the note while continually picking. Do this until the note goes dead. You need no more pressure than just a bit more than this to fret the note.
Also, try and play really slowly so you can accurately control your left hand fingers. I tried this for a couple of months last year and it really helped with my floating pinky - still not perfect, but much better than it was previously. Once the pinky has lifted too far off the fretboard, it's too late to fix it - so you have to be consciously aware of it's motion when your training it and ensure it lifts no further than necessary.