Solderless pickup connections came up recently in discussion, and instead of sharing them privately, I thought I'd start a new thread in case others may benefit. My method is not the only method for solderless connections, but it is the best I have found.
First, you need a crimp tool. Pololu.com has a great tool for a very reasonable price:
Crimp tool:https://www.pololu.com/product/1929There are lots of different styles of crimp tools out there, so for anyone who might say, "Oh yeah, I already have a crimp tool," just make sure yours can handle this size of connector. The one I linked to is solid, sturdy, and has ratcheting action. I like it.
You'll also need a wire stripper that goes down to at least 24 AWG. Pololu has those as well. I like their 16-26 AWG stripper:
https://www.pololu.com/product/161If you scroll down on the crimp tool page at Pololu, you'll see male pins, female pins, and housings that work with this crimp tool. However I would discourage purchasing these for guitar purposes, and instead get them from Mouser.com. The Pololu pins are inferior for audio signal, while the Mouser ones are gold plated and work wonderfully inside a guitar.
Female gold plated pins - Mouser.com: 538-16-02-0104http://www.mouser.com/ProductDetail/Molex/16-02-0104/?qs=sGAEpiMZZMs%252bGHln7q6pm%252bS0pk2Wo0XxhtdxrEhfd7w%3dMale gold plated pins - Mouser.com: 538-16-02-0117http://www.mouser.com/ProductDetail/Molex/16-02-0117/?qs=sGAEpiMZZMs%252bGHln7q6pm%252bS0pk2Wo0Xxt9hCdZlOXuQ%3d2-pin small housing (plug) - Mouser.com: 538-50-57-9002http://www.mouser.com/ProductDetail/Molex/50-57-9002/?qs=hSmm4fxMIuPN0%252b32zyqW%252bw%3D%3D2-pin housing receptacle (socket) - Mouser.com: 538-70107-0001http://www.mouser.com/ProductDetail/Molex/70107-0001/?qs=3%2Fy1uQ6JZnnrUEDOV9OGOA%3D%3DThe female pins go inside a small housing (plug), and the male pins go inside a housing receptacle (socket).
Male pins + socket go on the guitar side, and female pins + plug go on the pickup side.
Using 2-pin housing is important, even when you have 4 conductors and 4-pin housings are available. Reason being, the 2-pin housings will fit through wiring holes inside just about any guitar. Sometimes passage is a little tight, but it's very rare that I find a guitar that won't fit them. Note that the 2-pin housing product pages at Mouser show 6-pin housings. Don't be concerned -- those parts are the 2-pin versions. You can see them if you click the Documents tab then click the "3D PDF" link.
So you will need 2 pins per housing. Actually you will probably need some extras as you are learning -- there is a slight learning curve with the crimp tool and pins, so if you are starting out then you will probably waste a few pins as you get the hang of it.
The receptacles have a place for a latch, and there are latching plugs available. I rarely use the latching plugs, though. They are bulkier and you can run into clearance issues. Plus the non-latching ones are easily reversible, which makes troubleshooting and resolving phasing issues very easy.
Next time I do a pickup swap, I'll take some photos. I can expand this post into a tutorial later if people find it helpful.