OH YEAH - all your connections should be crimped, with a CRIMPING TOOL instead of just mashin' them together with a rusty pair of pliers (parts stores have 'em for less than $10 - try to find one similar to this:
IDEAL INDUSTRIES, INC. - Combination Crimp and Strip Tool ).
And don't just twist 'em together and tape 'em - unless you're good at soldering (or just like abusing yourself by having to do a job over and over and over again) and have a large-supply of heatshrink tubing. But, you likely wouldn't be seeking this sort of help if you knew how to do all that.
After each crimp, give the wire a good "tug" - actually try to pull it out. If you can dislodge it, better to find out your crimp-job was crap in the driveway than in a rainstorm on the side of the Freeway at Midnight.
If you like the belt-and-suspenders method of both a crimp AND a solder-joint (not really necessary, but... eh...) - Always ALWAYS Crimp FIRST - THEN solder the connection.
Solder will "cold flow", and if you solder a connector THEN crimp it, the heat/cool cycles WILL loosen the connection at odd times, and cause ghosts to haunt your electrical system.
Really pysses you off when that happens, believe-you-me.