Every time I see a video of someone doing push-ups, there's always someone in the comments saying about how the form is bad. I was always told my form was bad, but was never told what to do to improve it. Are push-ups just some Emperor's New Clothes kind of thing where nobody knows how to do one, but everyone needs to pretend to know so they don't seem like un-fit idiots?
Yeah, the diamond push up is a classic variation.
Also can raise your feet and/or add weights to make them more difficult