I personally have followed all of the standard advice, most of it listed above, but what was the ultimate solution was paying attention to if I slouch or not and correcting it.
The algorithm was: If I am slouching, even just a little bit, then I raise the monitor and repeat. There's a subtle but important difference than following suit to standards: I want the monitor height to not only be proper for when I sit straight, but I want it to promote me to sit straight.
The end results were my 22" monitors were positioned so my eye-level, while sitting straight, was about 1/3rd the way down the screen. The top of the screens were well above eye-level. Before, when the top of the screens matched my eye-level, I was still slouching; They were not high enough.
Now that I am done, the monitors feel very high off my desk. People make fun of how high they are.
It created another problem: I want to use arms to hold the monitors, instead of risers which take up all my desk room, and I have not been able to find any inexpensive ones that raise this high. The final height is about 11" off my desk. But, be aware that my desk surface is the level of my keyboard; I have no keyboard tray. My seat is fixed at a height which makes this ergonomically proper.
Hope this bit of personal experience helps.