Default value in my drop down list

I have two questions: 1) How do I create a default value in a Data Validation list? I have a number of carrier names in my list. However, 1 carrier is used 50% of the time so I would like that to be the default name unless the user selects a different carrier. 2) How do I make the font in a drop down list larger. It's hard to see some of the values in the drop down list when selecting from the list. Thank you!