Before you start digging in to a pile of connectors, crimp terminals, and wire, it’s a good idea to know what you’re getting into and Gogo:tronics has a great tutorial on how to crimp ...

Solder Seal Butt Connectors are stronger, waterproof, and easier to use than traditional crimp connectors.

I found great success by modifying $40 open-barrel ratcheting pliers (Del City, PN 990168) to crimp Packard 56 terminals (explained in the captions).