A bench vice works great for crimping IDC connectors, just make sure you get the cap lined up correctly before you crank it down. Some aluminum soft jaws or blocks of wood are handy to keep the vice from marring the connectors. If you're putting one on the end of the cable, crimp it with a bit of extra wire sticking out the other side, then slice it clean with a razor knife. Also make sure the connectors are all facing the right way around, it's difficult to remove one without breaking the clips.