Most people have a casual familiarity with the experience of being pulled over by police and being arrested on suspicion of driving while intoxicated. If the experience isn't first hand, chances are they have seen representations of it on television. The accused may be asked to participate in a field sobriety test, which often involves some sort of balancing act. They might be asked to take a breathalyzer test that involves blowing into a contraption meant to measure blood alcohol content. They might also be asked to submit to a blood test.
If stopped for suspicion of driving under the influence, an officer will want to check the person for signs of impairment. This almost always means the use of a breathalyzer test.