There is a tool if you are crimping a lot of them. Here: Heavy Duty Hammer Crimper
You can also use a 1/4" round steel rod and a vise - better than just smashing them with the vice - use the steel rod to focus the crimp. For large cast lugs, I usually drill a small hole in the end and use that to solder the connection.
When I can, I use adhesive-lined shrink tube - makes the connection waterproof. I buy the clear shrink tube - when it's sealed up, you can clearly see the connection and the wire color. (like the connections on the right in the picture).