Quoted from Rondogg:
have one of those IDC punch tools. They are really expensive for what they are. A mini flat head screwdriver served me well for 17 years
I bought one of those punch tools but a small screwdriver works better for me. One thing you need to be concerned about is damaging the wire sheating with a screwdriver. Make sure you don't tear the sheating to bad or the wire will move around a bit in the connector.