Recommend vs reality
Recommended: Most pre-workout supplements suggest that you do not take more than one scoop unless you no longer feel anything from one scoop and even then you should never take more than 2 scoops.
Reality: In a online survey about 60% of participants take more than one scoop, and about 10% take more than 2 scoops.
Recommended: Most pre-workout supplements recommend taking it roughly 20-30 minutes before exercise.
Reality: Most people do take their pre-workout at the recommended time with some taking it earlier at around 15 minutes. Some people would also warn against taking it when you might not be able to make it to your workout because it gives your body a very uncomfortable sensation.
Recommended: Nobody under 18 should be taking pre-workout.
Reality: While of course people under the age do take pre-workout most of the gym community at least those on Bodybuilder.com (a pretty popular fitness website) discourage those under the age of 18 from taking pre-workout. Instead they recommend eating the right foods.
Recommended: You should not mix pre-workout with other stimulating substances such as coffee, soda or tea.
Reality: Many people do mix their pre-workouts with sodas in order to try and mix the flavors, although it is easier said than done do to the carbonation of soda.
Recommended: It is recommended to read the directions and warning label before considering consuming pre-workout.
Reality: while practically everyone reads the directions it is not surprising that many do not read the warning label. it is practically 3 times the size with a lot of contents that wont apply to many people. Not to mention many just do not feel like reading a long block of text.
--Just keep in mind that this is not to criticize how others use pre-workout but to bring awareness to how pre-workout was intended to be used versus how the fitness community typically uses it.