A lot of people around here suggest a soak in Scrubbing Bubbles followed by a once over with an old toothbrush. I don't really know how often it's recommended.
I dip my razors in barbicide for 10-20 minutes before use for germ killing purposes.
As far as making them look nice, I do that whenever I change the blade. I remove all the soap scum with an old, soft toothbrush and a little dish soap.
I clean mine when the look like they need it, which is not too often. Usually just a hot water rinse is all I do. When they do look like they need a cleaning I'll sometimes take the blade out and use toothpaste and an old toothbrush to scrub out the hard to get at places. Works great and has yet to damage a razor yet. I'll also use scrubbing bubbles for a really good clean.
I clean my razors in a part of vinegar for 4 of hot water(not boiling).
Let your razor sit in that for 15 minutes after scrub them whit an old toothbrush.
After just rince the razor or parts under hot water.
I think that method is better for the environment.
My HD having been bought brand new requires very little maintaining. After my shave i simply pull it apart and with a cotton bud and hot water i clean the inside of the body and then dry it, the head gets rinsed in hot water and so too the rest of the razor..
Prior to each shave i generally half fill my sink with very hot (not boiling) water and let the razor sit in there whilst i have my shower
The two things I've tried are simple green and scrubbing bubbles. With each of these I used a toothbrush to scrub off the soap buildup.
The simplegreen didn't really seem to work. As I was cleaning with it, the plated parts of the razor seemed to shine better, but once it dried, it wasn't much better off than before. Might be I was using too diluted of a concentration.
The scrubbing bubbles worked like a charm. Not much I can say/add to it other than I will give the simple green another shot... it's supposed to be pretty benign when it comes to the environment, which I'm not sure is the case with scrubbing bubbles.
The other thing I've considered is diluted vinegar in boiling water. This really appeals to me as it would settle any qualms I have about the actual environmental impact of the simple green. However, I've seen mixed reviews as to whether this method is prone to harming chrome. In actuality, I'm sure simple green would have the same potential if you weren't sure to dilute and rinse properly.
As for how often: I've seen people that make it apart of their blade changing routine. I'm more of an "as needed" kind of guy when it comes to this... once a month or so, I'd say.