The Mamiya TLR 180 mm (or 18 cm) lenses are some of my favorite lenses that I have used. I have have three of them (as they seem to come in kits often). They were all great (one black, one silver 180 mm, and one silver 18 cm). I have pared down the trio to the one that had the most consistent and accurate shutter, as I couldn't tell any difference between the pictures shot with them.
As for tips, my advice is to shoot them at '500 or '250 if possible, when shooting hand held. If you really concentrate on it, you can get tack sharp shots at '125 as well. A left hand grip, pistol grip, or just a plain cable release can make this easier.
Also, pay close attention to your parallax indicator in the viewfinder ALL THE TIME. It moves quite a bit even when focusing on something only moderately closer than infinity.
These lenses are incredible. Super sharp, but without being overbearing about it. They have a very delicate quality about them, and tons of character in general. I have been told that they are all simply Carl Zeiss copies, but I have not confirmed this.
I suggest a lens hood as well.
As you move forward with expanding your C-Series system, I would not get hung up on getting black lenses as opposed to silver lenses for optical differences alone. My silver lenses leave nothing to be desired optically. The black lenses do have more modern shutters, for which parts are more readily available, and the apertures and shutter speeds are easier and more positive to set.