Your first court date is your arraignment. That is when the court reads the formal charges into the record and asks you how you plead to the charge. You are entitled to have a lawyer representing you on this case, and because this is a class 1 misdemeanor, which carries a maximum possibility of 6 months jail time and/or a fine of $2,500, you should have one.
If you cannot find representation by your court date, plead not guilty to the charges and ask the court for a continuance for you to come back with a lawyer. He will grant that to you.
Even though you may have actually sold alcohol to a minor as part of a police sting, you still have the right to plead not guilty under our law because our system of justice says you are innocent until proved guilty beyond a reasonable doubt. So a plea of NOT guilty is the only one that keeps all of your rights open so that you can get advised by counsel as to your rights and choices, have him negotiate a favorable disposition for you, or fight the case, all the way to trial if you wish. Any other plea would result in an immediate conviction. You should never plead guilty or no contest unless you know in advance what sentence you'll be getting in exchange for the plea.
If this is your first offense, you will likely end up just paying a fine, and you will almost certainly not have to worry about jail. But if it's at all possible, you don't want a misdemeanor on your record, and hopefully a lawyer can accomplish that for you.