Keeping in mind alcohol is a poison which can cause death it makes perfect sense that as soon as alcohol enters the blood stream, the body starts trying to get rid of it.  A relatively small percentage (perhaps as much as 10%) of consumed alcohol will be directly eliminated from the body in the breath, urine, sweat, tears, feces, etc., but the overwhelming majority of consumed alcohol is eliminated through metabolism.  Metabolism is simply a process of chemical change and approximately 90-95% of alcohol metabolism occurs in the liver at the hands of an enzyme known as alcohol dehydrogenase.  The body uses several different metabolic pathways in its oxidation of alcohol to acetaldehyde to acetic acid to carbon dioxide and water.

Although we can control the speed at which alcohol enters our bloodstream by slamming our drinks or sipping them slowly, and by drinking on an empty stomach or having a meal before drinking, there is essentially nothing that can be done to change the rate of elimination.  People tend to metabolize alcohol at a fairly consistent rate and the average rate of elimination ranges from about 0.015 to 0.018 g / 210 l of breath per hour.   That means if a person has a BAC of 0.15, it would take approximately 10 hours for that person to metabolize and eliminate all of the alcohol and return to a BAC of 0.00.  Drinking coffee may wake you up, eating some food will make you full, exercising will make you sweaty and showering will make you clean, but you need to understand that aside from making you feel better because you are awake, full, sweaty or clean, they do nothing to speed up the metabolism and elimination of alcohol from the blood. 

Of course, as with most things in life, there are exceptions to seemingly every rule, and elimination of alcohol is no different.  Chronic alcoholics may (depending on liver health) metabolize and eliminate alcohol at a rate significantly faster than the average rate.  Essentially, through years of practice, their bodies have become super efficient at breaking down and getting rid of alcohol.  Finally, like so many other things, as we age our ability to metabolize and eliminate alcohol quickly tends to slow.