Like everyone else says go to a parking lot(a flat, level one). If you are having trouble locating the engage point then stop your car. Put it in first and slowly let out on the clutch until the car starts to roll/the revs drop slightly, that is the engage point. Memorize it.
In a lot of other cars you can feel it but in the 370 due to the helper spring in the pedal you can't feel it at all. I have never owned an automatics car and I still have trouble in the Z. It's almost pure memorization unless you get the RJM pedal.
You should honestly just start a roll go maybe 5 mph, stop and repeat. Do this for a couple hours and shifting between gears will seem simple.
Also you asked what riding the clutch is. That is when you have the clutch partially engaged and rev the engine. This makes the flywheel and clutch plate slide against each other and will eat your clutch.
When I teach people I always make sure they understand what exactly the clutch assembly is and what it does. If you aren't 100% on that watch some YouTube videos this one I found real quick seems to give a pretty good explanation:
http://youtu.be/pqF-aBtTBnY