What can I do about an out-of-state underage drinking charge?

Well, you need to deal with it asap.  Can you ask anyone for help, like your parents?  Or another "adult" that you trust?  Did the citation/summons indicate a date that you have to appear in court?  Then you have to make sure that you go and an attorney should be appointed on your behalf.  What exactly is the charge?  Police officers can issue citations and do searches based upon observance and smell (like smelled alcohol on breath) but attorneys can refute the evidence if under the law you were entitled to take a test or they were required to give one to you.  You have to worry about suspension of your license, warrants for not showing up, etc.  Take this seriously.  Good luck.