My understanding is that you should always place a newly chipped loco onto a "Test track" before doing anything else.
As the resistor, which is in series with that section of track and the decoder, will prevent the decoder being destroyed due to possible wiring or decoder defects. In other words the decoder can't receive full power and it won't be blasted into space!
I'm thinking of using a section of siding which will be completely insulated from the rest of the layout.
I picked this up from the MRC site, as this is where my control system comes from... http://www.modelrec.com/resources/trainSou...progdecoder.pdf
What isn't stated is the value of the resistance?