It depends which CSS class you have placed around the container title. In the DNN Blue skin the class is:
.Head {
font-family: Tahoma, Arial, Helvetica;
font-size: 18px;
font-weight: normal;
color: #333333;
}
So you just need to change those settings.
If you are working with pure CSS skins, you can change the height easily in the CSS, if you are working with tables, you may need to look at the table that holds the title and check its height value - there maybe a css class assigned to the table where you can specify the height. - It all depends on the code from your skin.ascx / skin.htm file
Hope this helps, thanks,