Plain and simple - don't drink. — You cannot legally drink or purchase alcoholic beverages in Pennsylvania until you are 21 years of age. If you are caught buying, drinking, possessing, or transporting beer, wine, or liquor, you can be arrested. If convicted of underage drinking, you can be fined up to $300, jailed up to 90 days, or both. In addition, you will have a criminal record and lose your driver's license for 90 days.
If you are caught driving under the influence of alcohol (D.U.I.), it is a misdemeanor of the second degree, with a maximum penalty of up to $5,000 and up to two years in jail. If you are tried and convicted, you must pay a minimum of $300 and spend at least 48 hours in jail and pay other legal fees. In addition, you will lose your license for at least three months, possibly up to a year. Under Pennsylvania's Zero Tolerance Law, persons under 21 can be arrested and charged with a DUI even if their blood alcohol is .020 (any measurable amount of alcohol in your system.)
Pennsylvania, like many other states applies a “social host law” to people who decide to serve alcohol at a private party. Basically the law states that if you serve alcohol to a minor, and the minor injures either him/herself or someone else, the host can be sued and may have to pay damages to the injured person.
Parents who allow minors to drink in their home can also be charged with furnishing alcohol to minors, a charge punishable by at least a $1000 fine and up to a year in prison.