what is the best way to connect or splice resistors and contact leads to alarm cable?

All of the professional installers I know use Dolphin B connectors. Sometimes called beans or beanies. They are simple to use. You just slide them over the wires and crimp with pliers. There is no need to strip the wires, they have sharp edges inside which cut into the insulation on the wire to make a good connection.

i agree with wirepuller. they are sometimes listed as Dolphin Super-B wire connectors. they come in white or blue. the blue ones are sealant filled. they have an anti-corrosion moister barrier sealent inside to prevent corrosion. i always use the blue. you can get a bag of 100 for less than $10 at many electrical supply stores. they can be used with 16-24 AWG wire.