I Am A 23 Year Old College Graduate. How Do I Look Older?

I am currently applying to several professional job listings, and while I realize experience and education speaks for itself, appearance is also a large factor. I am often told I don’t even look 18, and even get raised eyebrows when I buy lottery tickets because the clerks don’t think I’m old enough. How can I change my appearance so as not to look like a 16 year old high school student and actually be taken seriously?