To vote in Maryland you must be a U.S. citizen, a Maryland resident, 18 yrs old by the next GENERAL election, and you must not be under guardianship for mental disability. Also, you can not have been convicted of buying or selling votes, can not have been convicted more than once of crimes of violence, and/or can not have been convicted of an infamous crime, unless, you have been pardoned, you have completed your sentence (1st conviction) or more than 3 years has passed since you completed your sentence (2nd or later conviction).
To find out more voter information go to:
Maryland State Board of Elections
Charles County Board of Elections