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?
It depends on what muscles you are trying to hit. The closer your hands are to each other, the more you are hitting your triceps as opposed to your chest. That being said, the most typical thing that people 'do wrong' is focus too much on their arms and not on keeping their 'core' tight and flat (basically focusing on abs and glutes). Otherwise, elbows should be at 45 degree angle to your body or parallel, as close as you can get. If they are at a 90 degree angle, you are doing some weird stuff to your shoulders that is better accomplished through other means.
That being said I hate doing pushups and only use them for balancing excersize, otherwise everything you can accomplish with pushups is easier to accomplish through benching.