For electrical terminals it's best to use a crimper that is intended for non-insulated terminals. (I know this sounds nuts but I'll try to explain)
The garden variety crimpers for insulated terminals will consist of two cresent shaped dies and crunch both sides of the terminal barrel over the wire. These have a bad habit of not providing a good solid crimp to the wire especially in the case of stranded wire.
Non-insulated crimpers have one side with a half circle with a point on the other side.
something like this: > ) as opposed to this: ( )
This point punches into the terminal barrel and actually causes less distortion to the insulator than the "cutting in half" effect of the insulated crimpers. It's been my experiance that it also provides a rock solid retention of stranded wire. A good place to look for this type of crimper is in the fishing dept. (used for leader barrel crimps) When using these crimpers you want to punch into the side of the barrel opposite of the seam. (typically the bottom of the connector)
Also terminals with nylon insulators as opposed to the plastic ones are preferrable especially in outside areas of the car. Nylon terminals typically have a transparent appearance. The nylon is much more resistant to splitting, heat, and chemical breakdown.
A loose crimp can be a real bear to track down, especially on the side of the highway. Take those insulated crimpers and toss them in the trash. (or keep them handy for someone that wants to borrow your tools)
Here's what your looking for:
Grainger Industrial Supply: Crimping Plier 3KH45