In addition to DaVinciLe0's method of urinal selection, an alternate method is sometimes needed for urination locations in which the urinals don't line up in a row and/or don't provide adequate job security. Also, other provided facilities (sink, shower) can affect the urinal selection. (After all, who would want to take a whiz directly next to a steaming shower?)
In my college residence hall at Florida State University the bathrooms are shared by approximately 30 college students. The ones on my floor are notoriously filthy on the weekends because that is when the custodians are not there and the students are inebriated and vomiting - generally, in the sink and in Toilet #3.
To facilitate the discussion I provide Figure 1:
.---|(FAN)| |---------| | |----.
| | |( ) > {]2|
|* | |(@@) > {]1|
| 3 | 2 | 1 | *|
| | | | | 1 | 2 | 3 |
| | | | | | | |
| | | | | B | W | W |
| || | || | || | | (0) |(0)| (0) |
`------------------'{|}----------------
KEY:
{|} - door
(0) - toilet (B=black rounded "public-style" seat, W=white molded homely seat)
{] - urinal
|| - shower
* - weird fan machine
(FAN) - window vent
@@ - sink and vanity
> - raised urination area
** - On the other side of the building, the diagram is reversed.
Now, imagine this common situation. A resident is peein' at Urinal #1 or #2. Notice that there is no divider between the two urinals, they are in fact attached at the midsection similar to Siamese twins. Obviously it is unheard of for two residents to use the urinals simultaneously due to the inherent exposure. The second resident will immediately enter Toilet Stall #1 - the only one with the rancid seat (with the exception of vomitus-covered #3 on weekends) - and urinate there. This occurs without any previous discussion of any kind. I have never observed a time where both either Urinal AND Stall #1 would be in use at the same time. My only guess as to what would happen would be that the third person would stand by the vanity area for a moment and pretend to examine hair or face, etc. until either allowed urination zone becomes available.
So, unlike the giant restroom with an entire row of urinals, selection of a urination collection instrument becomes quite a mind-boggling task when two urinals are provided with no security divider. I don't quite understand why they didn't build just one urinal.