Curly, torque wrenches are great for this stuff, but totally unnecessary. If you look at brand new equipment, on many fittings, you see where they made a mark from one fitting to another with a magic marker or a paint stick. They tighten finger tight, make a mark down both fitting flats, then turn the fitting a certain amount of flats based on fitting size.
Here is a good rule of thumb for JIC and flat-faced o-ring and straight thread o-ring:
-4 and -5 fitting, 2 hex flats.
-6, 1 1/4 hex flats.
-8 and larger, 1 hex flat.
Keep in mind, this isn't complete turns, it is rotation of the hex flats, basically, 1/6 of a turn.
Just remember, if you undertighten, you can always tighten. Once you overtighten, the damage is done.