I'm going to go ahead and suggest the use of some good sense (ref. ADM) regarding ext. power switch manipulation on the CRJ 200/700/900. This is good for all airplanes that utilize ground power in this way as this is a very basic check. Of course this assumes that time or operational conditions require you to even need ground power in the first place.
This takes much longer to read than the few seconds to actually do so please, hang in there on this one!
So, you taxi into your assigned spot. One of your generators will be left running until your power gets plugged in. Don't just use the switchlight for verification, select and monitor the appropriate EICAS page. That way you'll know not only when it's plugged in, but most importantly if it's of the correct voltage and frequency and if it's stable. You'll also know if the switchlight's bulb is blown or a bit loose, short of doing a lamp test.
Now, assume all is looking good up to this point. Do -not- just throw that thrust lever to shutoff or ram that apu stop button. Leave it running for now. The stability of the ground power must be tested to avoid potential and unnecessary wear that will lead to a premature failure. This has nothing to do with the airplane "liking" it. The EICAS can show it good all day long; the system has no way of evaluating and warning of the stability of it. This is the pilot's job. Sometimes it will show on the EICAS by observing fluctuating readings, in which case you stop here and leave it alone until the passengers are off. If the display shows stable, continue as follows.
First ensure the ext. power switchlight is pressed in. Next, take your operating generator's switch and move it to "off/reset" to make the system logic switch to ground power. Keep your hand on the switch. Most importantly now, -wait about 5-10 seconds to see if the flow remains stable-.
I'll point out the critical op first. -If at any point you hear and see signs of the power flickering off and on, immediately move your operating generator's switch back on to restore a smooth flow of power to your system-. Leave it as is until the deplaning is complete and deal with it then. Rapid off/on power surges are incredibly damaging to your electrical system. Doing this minimizes that damage. You also don't want power issues while you have passengers aboard.
If the power turns out to be stable, -before you move the gen switch again- first shut down whatever is driving your on-board generator (engine/apu). Wait for the generator's output to drop sufficiently enough so system logic won't try to pick it up again, then move the gen switch to whatever your carrier's normal position for that switch is and you're done.
Congratulations, you just protected your electrical system! This only takes at most 5-10 seconds of your time so there's no good reason to omit it. Why should you care? Consider the following:
The most important reason to most pilots will be the delay it will cause if something breaks.
Got plans and would like to make your overnight on time? Last day and you're a commuter?
Less selfishly, do you care about your passenger's plans? What about your carrier's performance numbers?
What about the cost of repairs?
What about lost revenue due to lack of equipment?
Etc., etc, etc?
Remember, use good CRM/ADM (use APU, require a good GPU, hot ops [engine running], etc.). Take these terms seriously. They're not there as something to just "check the box" or ignore during initial/recurrent. Every possible situation is not in the book. That's why they hired you. Protect the airplane. Remember, at the very least it's your ride too.