There's one grave decorating sin that's incredibly easy to accidentally commit, and it throws the whole scale and balance of a room immediately out of whack. Luckily, it's just as easy to fix, and the remedy requires only a few seconds and a couple of tools.
The sin in question? Hanging art too high. There's a tendency for people to err on the side of height when hanging art, resulting in top heavy rooms and strained, craned necks.
Remedying this issue is simple: just grab a measuring tape, a hammer, and some nails, and commit to memory the following rules of thumb:
In general, art should be hung '57" on center,' meaning the horizontal center of the artwork should hang at 57" from the floor, which is the average eye height of a standing person.
While 57" from the floor is a general standard, one should always take into account how people actually use the room in which the art will be hung. If it's a space used mostly while guests are seated or lounging (like a dining or TV room), then you want to center the art on a seated person's eye line.