There are several methods to cut concrete retaining wall blocks. The best is a gas concrete saw, but they are usually too expensive to buy or rent for homeowners. Plus you can't just rent a gas saw for one day, as you typically need to cut blocks on an irregular schedule throughout your project as you build it, not just on one day. This video shows one option, using a circular saw with a diamond masonry blade. It makes a very nice, clean cut. You also use a wide chisel and four pound mallet to break off chunks, or trim bumps off the block, or to make the final split in the block. Note that this method produces a LOT of fine dust, and you must use good breathing protection, along with all the other safety equipment/clothes I recommend in the video. You can get all these tools and safety equipment at your local home improvement store.
Beginning music is by Vanessa-Mae, song is Bach Street Prelude:
http://en.wikipedia.org/wiki/Vanessa-Mae
