Those expensive press tools that Yiannis shows are the "official" way to attach ribbon cables to those IDC connectors. They're not strictly necessary, though. All you really need is the ability to press straight down on the connector at a 90 degree angle.
Channellock pliers work better on IDC connectors than normal pliers since their fulcrum is farther away and their jaws are longer. Normal pliers tend to only press on one side or the other, and the pins in the middle don't always get connected as well.
An important note with these DIP IDC connectors is that the pins aren't attached to the plastic part very securely. It's easy to push a pin completely out of the socket, or to end up with pins that are no longer the same length. Pliers tend to move or bend the pins, so I've found it best to put the socket in a breadboard first. The breadboard will hold the pins straight and prevent them from moving too much. I usually place a piece of scrap cardboard on top of the ribbon and use that to press the cable down. Once it's attached, I make another pass using the edge of my fingernail or a flat-headed jeweler's screwdriver to make sure each conductor is wedged all the way down between the spikes. Before you put the cap part on, remove the socket from the breadboard and set it on a flat surface to verify that all the pins are still the same length. If one shifted slightly, you can gently adjust it with needlenose pliers.
If you already have a PanaVise, they make a base plate specifically designed to accommodate the pins of DIP components.