Title pretty much says it. You are wiring a house…you have a bunch of left/right/fat bastard ground on the bottom. Does it go to the bottom or up?
IOW: How should you orient the outlets?
Some towns have code for this so it varies by municipality.
In general, today it is considered safer to have the ground up. In the past the ground was down. If sideways mount, common (not hot) should be up.
One reason for the change, there has been a few cases of metal wall plates slipping and shorting across the hot and common blades of a plug.
There are probably other reasons.
Oh, you are driving a stake through my heart. Ground is down.
I replaced a few outlets in my house and figured I’d “do it right” and put the ground on top.
Half the stuff I plug in is all screwed up because the device / cord is designed assuming ground is down. I have upside down nightlights, right angle plugs that turn upwards instead of downwards, I wound up having to turn the plugs back around for my own sanity.
It only really matters if you town has a code for it and inspects such for COs.
Check with your town before making any changes.
My current home was built in the 60s. Most of the outlets are ground down. My town either approves or doesn’t care. This is most common. The Doesn’t Care part.
So, being GQ, ground is up? My grandfather was wrong?
A dead short to neutral, at least isn’t a big deal, other than the spark and the noise and possibly ruining whatever shorted the prongs. What’s even more dangerous is if the thing doesn’t short out, but just rests on the hot side. You go to grab is and and shocked.
So much of this could be fixed, and it wouldn’t matter what orientation the outlet was in if we used the system in other countries. Without even getting into the new safety measures that require the ground prong to be inserted first, but just the fact the insulation on the plug extends down far enough that it’s not possible for the conductor to be both exposed and live.
Please read my full post again. In the past, the ground was down. Over the last 30-40 years towns have been changing code to Ground is up.
Good point Joey_P and one I learned but since forgot.
That seems to be the GQ answer. In 1988 when he would put a plug of tobacco in his mouth and say, “Son, ground is down to the ground” he was correct for the time.
He probably was correct. Though in at least one town in Monmouth County, NJ he would have been wrong already. 
When he learned it, I’m 99.9% sure he was correct.
And as I think back. In 1988, in the Navy, ground was still down.
And at the time, I was putting it in the way he told me.
I vaguely remember a thread about this from years ago and that possibility was offered as the reason for ground up. It seems really implausible to me. Has it ever been documented as happening in the real world?
Actually, I’ve seen the char marks on the metal plate and plug blades. It has happened. Part of the reason why that reason stuck with me.
And to follow up on this, has there been a single house fire, or even a single incident because someone’s redneck grandfather chewing tobacco wired an outlet with the ground down?
This is the first time I’ve ever heard there was a preference for the orientation of ground, let alone code. My house was built 14 years ago and all the plugs are ground down. But then, this is Canada.
A lot of clever ads about things like electrical safety show the ground down, but then the “clever” is they make the socket look like a “shocked expression” face.
I’ve never heard of such.
Though I can tell you, that plug-in air-fresheners are/were one of the leading causes of house fires. At least for a few years, up there with candles.
Well, at least no tobacco chewing old guys did anything. I did wonder at the time and asked why if it was in a controlled box why it mattered. I got the look, so I put ground down. 
ETA: And have for the following 32 years.
I really wouldn’t worry about it unless you get dinged on inspection by your town.
I’ve seen exactly one house get dinged for it on CO inspection. I’ve seen only one inspection for Electrical Work ding a company I worked for, for it. Now I’m not a working electrician, but I’ve kept my hand in it for a long time.
I just double-checked. The NEC The National Electrical Code doesn’t have a preference. Any orientation is OK as far as they’re concerned.
Good. I am starting a “ground is down” march…coming soon to your town! 
Also, the argument is that if you drop something conductive and the plug isn’t all the way in (worked its way loose or wasn’t plugged in properly to begin with), the dropped item will short across the hot and neutral if the ground is down. It’s not just wall plates.
On the other side of the fence, the argument for the ground being down is that the way many people will grip the plug, they are more likely to accidentally touch one of the contacts with their index finger on the bottom of the plug. Having the safety ground on the bottom reduces the chance of an accidental shock.
In some cases, as the electrical contacts in the outlet wear. you’ll get better mechanical grip in the worn outlet if the ground is up. In other cases, especially right-angle plugs, having the ground up puts more mechanical stress on the plug and is more likely to cause a failure in the cord. So ground up or ground down both have arguments with respect to mechanical strength and wear.
Some wall warts and other devices are designed for an outlet with the ground on the bottom.
The NEC doesn’t specify ground up or ground down. As was already mentioned, local coded might. I used to live in an area where it was specified that the grounds had to be down. The next town over specified that the grounds had to be up.
If your local codes do not specify which way they should go, you should at least be consistent. Don’t have some outlets ground up and others ground down.
Sometimes if you have switched outlets (outlets turned on and off by a nearby wall switch), those outlets will be installed upside down compared to other outlets in the home, just to give a visual indication that those are outlets are different.