This depends on the actual crime. Two different crimes may both be classified as a class A misdemeanor yet carry different punishments. Additionally, it will depend upon whether you are being charged by a municipality or the state.
Usually, the statute will identify a range for your punishment. For instance, the minimum fine may be $100, and the maximum fine may be $1,000 according to the statute. It will be up to the prosecutor and judge as to what the actual fine amount is. It will also be up to the prosecutor and judge as to whether you receive any jail time or other punishment. Their decision will be based upon the nature of the crime, your criminal history, and a variety of other factors which are specific to you and this particular charge.
For first time offenders, you'll often receive a fine that is closer to the minimum amount and you won't have to serve any jail time. It's also possible that the court in which your charge is brought has a court referral program for first time offenders. This would mean that you would take court ordered classes, perform community service, etc., in order to have the charge removed from your record. However, you will need to speak with an attorney in order to determine what the possible punishments are for your particular crime in that jurisdiction.
Class A misdemeanors are punishable by up to 364 days in jail and a fine of up to $2500. With any misdemeanor, including the Class A misdemeanor, the sentence a defendant receives can include other terms such as probation, substance-abuse treatment, and community service work.
While you may get some leniency because of your clean record, don't underestimate the importance of having an experienced defense attorney. Look for someone who focuses their practice on criminal defense and has handled your type of case before. Stay local - an attorney familiar with the courthouse, judges, prosecutors, etc., can have an advantage. If you need a referral, feel free to give me a call. 1-800-517-1614. I'd be happy to point you in the right direction.