best way to make connections

Quality terminals and ratchet crimpers make good connections. Good terminal are more expensive and are not typically found at auto part stores. I order supplies from Waytek.

Beware soldering aneals the wire at edge of joints, and will fail more than properly crimped connection. Heat shrink, wire looms and tie wraps help support connections from vibrations.

Good points that you don't see mentioned.
I also try and support the wiring to the connections so the weight of the wiring/harness isn't pulling on them. We all seem to forget that things move.