In my very limited experience the major falling cause for clipping newbies is that they unclip one foot at a stop but then accidentally lean too far in the clipped in direction. Seen it happen a lot. So, my number one tip to new clipless riders is to unclip both feet every time, and don't be afraid to unclip early and just pedal unclipped for a bit.

As far as shoes go, I have not encountered any that I would want to wear all day. I know a lot of folks swear that Shimano's sandals are comfortable enough for this, but depending on what you do for a living those may not be work appropriate.