One of the most crucial things that you need to do when you use a bathroom is to remember to wash your hands (some of us seem to have more problems in this area than others but this is not the place to name names). At home this is a simple task, but the situation is often much more complicated in a public washroom where you have a myriad of sinks from which to choose.
If the sinks are on the same wall as the urinals:
Try to choose a sink which is far away from the nearest urinal. Just like someone peeing doesn't want someone else to pee beside him, they also don't want someone to wash their hands beside them. And even if the urinals are empty, do you really want to wash your hands right beside them?
If the sinks are on a separate wall from the urinals:
Try to choose one that's away from high traffic areas like the garbage or towel dispensers/hot air blowers. Otherwise you just end up bumping elbows with people who are trying to use these devices.
And of course try to find one which is clean:-)