Here is the scoop on the AMP plugs as per Wikipedia:

"There are two types of 8P8C plugs, sockets, and diesets (used for crimping): Western Electric/Stewart Stamping (WE/SS) and Tyco/AMP. While both types look remarkably similar, they are exclusive and cannot be interchanged. Tyco/AMP 8P8C plugs are proprietary, and have smaller spacing between contacts than the WE/SS style. As a result, using a WE/SS 8P8C crimp dieset on a Tyco/AMP 8P8C plug will crush the top of the connector, and vice versa. While the WE/SS 8P8C plug is more common than Tyco/AMP, it is still important to know what style is being used to avoid damaging the plug during crimping."

I dont do alot of crimping either but when I do I have very few problems. I do as Clinton described and squeeze the hell out of em and then do it a couple more times just for good measure. I use a scissors to do my final trim and haven't had any problems with getting the wires to fit. I prefer a ratcheting type crimper. The first crimper I started with was not of the ratcheting type and seemed to have quite a bit of play in the handles thus causing the actual crimping pins to not line up in the die. That caused quite a few busted plugs and a lot of frustration. Ive used a ratcheting crimper from Ideal for quite a few years now and it works great.